JUSTICE TURNER delivered the opinion of the court:

In February 2002, petitioner, Steven Mark Sobol, fileda petition for modification, requesting that he not be requiredto move with the minor children, Brett Isacc Sobol (born November1989) and Valerie Gale Sobol (born May 1992), to Eagle County,Colorado, where respondent, Jill R. Sobol, resided. After athree-day hearing, the trial court granted petitioner's petition. Respondent appeals, contending (1) the trial court imposed thewrong standard for modification, (2) the trial court erred inadmitting prejudgment evidence, and (3) petitioner failed to meethis burden of proof. We affirm.

The parties were married in July 1987. In March 1998,petitioner filed a petition for dissolution of marriage. OnNovember 8, 2000, the trial court entered a judgment of dissolution, granting petitioner custody of the minor children withrespondent having reasonable visitation rights subject to theterms of the November 1, 2000, marital settlement agreement(Agreement). The Agreement provided the following:

"Because the parties believe that thechildren will be best served by having frequent, regular contact with both parents,[petitioner] shall relocate himself and thechildren to Eagle County, Colorado, by September 2002, hereinafter referred to as the'relocation date.'"

The Agreement then set forth different visitation schedules forrespondent prior to the relocation (Illinois visitation schedule)and after the relocation. Additionally, after the relocationdate, petitioner was to remain the legal custodian of the minorchildren, but the parties were to cooperate in making all important decisions regarding the children's "upbringing, health care,education, religious training, and extracurricular activities."

In June 2001, petitioner married his present wife, JillE. Sobol. Petitioner, his present wife, the minor children, andpetitioner's five-year-old stepdaughter, Carlie, live in a homein Forsyth, Illinois. Petitioner and the minor children haveresided in the home since January 2000. Petitioner is a board-certified ear, nose, and throat specialist with subspecialtytraining in head- and neck-tumor surgery and skull-base surgeryand maintains a medical practice in Decatur, Illinois.

Respondent lives in a home in Edwards, Colorado. Shemoved to Colorado in August 1999 with the minor children, wholived with her until Christmas 1999. Respondent works part-timeas a merchandiser and, at the time of the hearing, was negotiating a partnership interest in a store.

On February 7, 2002, petitioner filed a petition formodification, requesting that he not be required to move toColorado. In April 2002, respondent filed a petition to dismisspetitioner's petition, asserting petitioner failed to allegeserious endangerment under section 610(a) of the Illinois Marriage and Dissolution of Marriage Act (Act) (750 ILCS 5/610(a)(West 2000)). That same month, the trial court denied respondent's petition to dismiss. In May 2002, respondent filed amotion to reconsider. In June 2002, respondent filed a petitionto compel compliance with the dissolution judgment.

Beginning in July 2002, the trial court held a hearingon the motion and two petitions. Petitioner testified on his ownbehalf and presented the testimony of respondent as an adversewitness; Carol Jones, petitioner's nurse; Rita Colee, petitioner's neighbor; Mallory Nelson, petitioner's neighbor; Dr.Lisa Orf, the minor children's psychologist; petitioner's presentwife; Julie Mikels, the minor children's baby-sitter and familyfriend; and Nalini Taylor, mother of one of Brett's friends. Respondent testified on her own behalf and called petitioner asan adverse witness.

In total, the trial court heard from eight witnessesover three days. The parties are well aware of the evidencepresented at the hearing, and it need not be set forth in detail.

In October 2002, the trial court entered a lengthydocket entry, finding the standards of section 607(c) of the Act(750 ILCS 5/607(c) (West 2000)) applied to the case, determiningthat remaining in Illinois was in the children's best interests,granting petitioner's petition for modification, and denyingrespondent's motion to reconsider and petition to compel compliance with the dissolution judgment. This appeal followed.

Respondent first asserts the trial court applied thewrong legal standard in this case. The appropriate legal standard in evaluating a modification of a marital settlement'srelocation provision is a question of law, and we review de novosuch questions. See Illinois Licensed Beverage Ass'n v. AdvantaLeasing Services, 333 Ill. App. 3d 927, 932, 776 N.E.2d 255, 260(2002).

The Agreement contained a modification clause thatprovided a party could petition the court to modify the custodialand visitation provisions of the Agreement where "a substantialand material change in circumstances of either party or eitherchild, or both" occurred. However, neither party asserts thisprovision applies, and the trial court found it was not bound bythe provision. Accordingly, the trial court's notation that theAgreement's modification provision was "the key to the presentcontroversy" was irrelevant to its ultimate determination of thecase.

We agree with the trial court that the Agreement'smodification provision is not controlling. Section 502(f) of theAct (750 ILCS 5/502(f) (West 2000)) allows a marital settlementagreement incorporated in the dissolution judgment to expresslypreclude or limit modification of its terms "[e]xcept for termsconcerning the support, custody[,] or visitation of children." Accordingly, the trial court had the right to modify the Agreement pursuant to the provisions of the Act. See In re Marriageof Loffredi, 232 Ill. App. 3d 709, 714-15, 597 N.E.2d 907, 911(1992) (addressing modification of settlement agreement'scollege-expenses provision).

The modification sought is not expressly governed by aprovision of the Act (750 ILCS 5/101 through 802 (West 2000)). The parties each assert a different statute applies, and thetrial court found a completely different statute was applicable. Thus, we will review the relevant provisions of the Act.

On appeal, respondent asserts section 608(a) of the Act(750 ILCS 5/608(a) (West 2000)) is applicable to this case. Section 608(a) provides as follows:

"Except as otherwise agreed by the parties in writing at the time of the custodyjudgment or as otherwise ordered by thecourt, the custodian may determine thechild's upbringing, including but not limitedto, his education, health care[,] and religious training, unless the court, after hearing, finds, upon motion by the noncustodialparent, that the absence of a specific limitation of the custodian's authority wouldclearly be contrary to the best interests ofthe child." (Emphasis added.) 750 ILCS5/608(a) (West 2000).

In the trial court, respondent asserted that petitioner's petition was a modification of custody under section 610of the Act (750 ILCS 5/610 (West 2000)), and thus it should bedismissed because petitioner brought it within two years of acustody judgment (see 750 ILCS 5/610(a) (West 2000)). Undersection 610(a) of the Act (750 ILCS 5/610(a) (West 2000)), absenta stipulation by the parties, such a motion can only be broughtwhere the court permits it based on "affidavits that there isreason to believe the child's present environment may endangerseriously his physical, mental, moral[,] or emotional health." 750 ILCS 5/610(a) (West 2000). Petitioner did not file anyaffidavits.

Petitioner asserts that this case is similar to aremoval case under section 609 of the Act (750 ILCS 5/609 (West2000)). Pursuant to section 609, a court may grant leave to theminor children's custodial parent to remove such children fromIllinois whenever such removal is in the children's best interests. 750 ILCS 5/609 (West 2000).

The trial court found the standards of section 607(c)of the Act (750 ILCS 5/607(c) (West 2000)) applied. Respondentasserts that if section 607(c) is applicable, then the trialcourt restricted her visitation rights. Section 607(c) allows atrial court to modify a parent's visitation rights whenevermodification would serve a child's best interests, but prohibitsa trial court from restricting a parent's visitation rights"unless it finds that the visitation would endanger seriously thechild's physical, mental, moral[,] or emotional health." (Emphasis added.) 750 ILCS 5/607(c) (West 2000).

In this case, petitioner filed a petition, requestingthe court to modify the marital settlement agreement by notrequiring him to remove the minor children from Illinois toColorado. Ordinarily, a custodial parent will file a petition toremove a minor child from Illinois. Under section 609 of the Act(750 ILCS 5/609 (West 2000)), the trial court may approve such aremoval when it is in the child's best interests. Section 609governs removal even when an agreement purports to limit theright of removal. See In re Marriage of Yndestad, 232 Ill. App.3d 1, 7, 597 N.E.2d 215, 219 (1992). While section 609 does notexpressly govern the current situation, the petition addresses apotential out-of-state move, and thus we find section 609 of theAct contains the applicable standards. See Falk v. Falk, 77 Ill.App. 3d 13, 15-16, 395 N.E.2d 750, 752 (1979) (applying thesection 609 standard, even though not expressly applicable, to aremoval of a minor child from the agreed area to another city inIllinois).

Section 609 of the Act applies, even though uponrelocation respondent was (1) to participate in all importantdecisions regarding the children's upbringing as allowed undersection 608(a) of the Act (750 ILCS 5/608(a) (West 2000)) and (2)to have a substantial increase in visitation with the children. Illinois courts have recognized that removal affects anoncustodial parent's visitation rights and contractual rights toparticipate in the minor children's upbringing. See In reMarriage of Eckert, 119 Ill. 2d 316, 327-28, 518 N.E.2d 1041,1045-46 (1988) (visitation rights); Yndestad, 232 Ill. App. 3d at7, 597 N.E.2d at 219 (custodial rights). However, that impactdoes not invoke the modification-of-custody standards of section610 of the Act (750 ILCS 5/610 (West 2000)) (Yndestad, 232 Ill.App. 3d at 6-7, 597 N.E.2d at 219) or the standard for restricting visitation pursuant to section 607(c) of the Act (750 ILCS5/607(c) (West 2000)) (see Eckert, 119 Ill. 2d at 327-28, 518N.E.2d at 1045-46 (examining only the impact on visitation)). While those standards do not apply, the trial court is to consider the modification's impact on the other parent's visitationand custodial rights in analyzing the child's best interests. See Eckert, 119 Ill. 2d at 327-28, 518 N.E.2d at 1045-46(noncustodial parent's visitation rights); Yndestad, 232 Ill.App. 3d at 7, 597 N.E.2d at 219 (impact of proposed removal onjoint custody rights of nonresidential parent).

Moreover, the clearly-contrary-to-the-best-intereststandard of section 608(a) of the Act (750 ILCS 5/608(a) (West2000)) does not apply. That standard applies where thenoncustodial parent files a motion, seeking to limit the custodial parent's statutory authority to make decisions regarding theminor child. See 750 ILCS 5/608(a) (West 2000). In this case,petitioner, the minor children's custodial parent, filed themotion.

Although the trial court found this case was a modification of custody under section 607(c) of the Act, the trialcourt noted the question presented was "whether the best interests of the parties['] children would be served by remaining inIllinois or moving to Colorado." That question is the same onethe trial court would have addressed under section 609 of theAct. See Eckert, 119 Ill. 2d at 325, 518 N.E.2d at 1044 (inremoval cases, the paramount question is whether the move is inthe child's best interests).

Accordingly, we find that, while the trial courtapplied the wrong statute, it did not apply the wrong legalstandard.

Respondent next argues the trial court erred in admitting evidence of events prior to the entry of the dissolutionjudgment. The admissibility of evidence lies within the trialcourt's sound discretion, and a reviewing court will not reversethe trial court's decision absent a clear abuse of discretion. In re Marriage of Rudd, 293 Ill. App. 3d 367, 371-72, 688 N.E.2d342, 345 (1997).

The specific prejudgment evidence that respondentalleges was admitted in error is Dr. Elizabeth Scott's custodyevaluation report that was issued before the dissolution judgment. While respondent's counsel made a continuing objection toprejudgment evidence, the record clearly indicates respondent'scounsel stipulated to the report's admission into evidence. Aparty forfeits his right to complain of an error to which heconsented. McMath v. Katholi, 191 Ill. 2d 251, 255, 730 N.E.2d1, 3 (2000).

As to prejudgment evidence in general, section 609 ofthe Act does not prevent a court from considering known, prejudgment evidence like the modification-of-custody provision (750ILCS 5/610(b) (West 2000)). Moreover, the Supreme Court ofIllinois has held a trial court should hear any and all relevantevidence in making a removal determination. In re Marriage ofSmith, 172 Ill. 2d 312, 320, 665 N.E.2d 1209, 1213 (1996);Eckert, 119 Ill. 2d at 326, 518 N.E.2d at 1045. Additionally,the party asserting res judicata has the burden of proving theprecise issues had already been considered. In re Marriage ofWade, 158 Ill. App. 3d 255, 263-64, 511 N.E.2d 156, 162 (1987). Here, respondent failed to do so. Accordingly, we find the trialcourt did not abuse its discretion in admitting prejudgmentevidence.

Respondent last contends the trial court's judgment wasagainst the manifest weight of the evidence in that petitionerfailed to meet his burden of proof. We disagree.

Under section 609 of the Act (750 ILCS 5/609 (West2000)), a trial court may only approve a custodial parent'sremoval of the minor children from Illinois when the approval isin the children's best interests. The burden of proving suchremoval is in the children's best interests is on the partyseeking removal. 750 ILCS 5/609 (West 2000). Thus, petitionerbore the burden of proving that remaining in Illinois was in thechildren's best interests. A determination of a child's bestinterests cannot be reduced to a simple bright-line test butrather must be made on a case-by-case basis, depending, to agreat extent, upon the circumstances of each case. Eckert, 119Ill. 2d at 326, 518 N.E.2d at 1045. A trial court's determination of what is in a child's best interests should not be reversed unless it is clearly against the manifest weight of theevidence and it appears that a manifest injustice has occurred. Eckert, 119 Ill. 2d at 328, 518 N.E.2d at 1046.

In removal cases under section 609 of the Act, thesupreme court has identified five factors that should be considered in determining whether removal is in a child's best interests. Those factors are (1) whether the proposed move willenhance the quality of life for both the custodial parent and thechildren, (2) whether the proposed move is a ruse designed tofrustrate or defeat the noncustodial parent's visitation, (3) themotives of the noncustodial parent in resisting removal, (4) thevisitation rights of the noncustodial parent, and (5) whether areasonable visitation schedule can be worked out. In re Marriageof Shaddle, 317 Ill. App. 3d 428, 433, 740 N.E.2d 525, 530(2000). While this case is not an ordinary removal case, theabove factors set forth some of the issues that should be considered in determining the children's best interests.

As to the quality of life of the custodial parent andchildren, this court has found it is proper for the trial courtto consider the financial and emotional well-being of the custodial parent. See In re Marriage of Eaton, 269 Ill. App. 3d 507,515, 646 N.E.2d 635, 642 (1995). Petitioner testified that hismedical practice was important to him and he wanted to continueto work. He had tried to obtain similar employment in Coloradobut could not find a position. Respondent contends that petitioner does not need to work for financial reasons. However, therecord indicates petitioner also needed to work for his emotionalwell-being.

Next, the evidence shows that neither party had improper motives for seeking or opposing the modification. Petitioner had not tried to frustrate respondent's visitation, andthe evidence showed he tried to provide visitation to meetrespondent's schedule. Additionally, he purchased a home inColorado and tried to find a job there. Respondent opposed themotion because she would have longer and more frequent visitationwith the children if they lived in Colorado.

Regarding respondent's visitation, the parties alreadyhave established a reasonable visitation schedule addressing thechildren living in Illinois. While respondent desires theincreased visitation a move to Colorado would provide, respondenthas not exercised all of her visitation under the Illinoisvisitation schedule. Petitioner testified on several occasionsrespondent returned the children early. Colee testified she hadwatched the children while respondent went out with friends inDecatur.

Additionally, the record shows petitioner has allowedrespondent to have the children when she has requested. Petitioner even attempted to provide respondent with additional timewith the children while he had a speaking engagement in Coloradobut respondent made other plans.

Pursuant to the Agreement, when petitioner moved toColorado, petitioner was to retain legal custody of the childrenbut the parties were to cooperate in making all important decisions regarding the children's upbringing, health care, education, religious training, and extracurricular activities. Accordingly, the impact on respondent's right to participate inthe decisions regarding the children's upbringing should also beexamined. See Yndestad, 232 Ill. App. 3d at 7, 597 N.E.2d at 219(addressing joint custody).

The Agreement also included a "parental cooperation"section that was to apply both before and after relocation. Petitioner testified that respondent has violated five out of thesix provisions included in that section. Petitioner, petitioner's present wife, Dr. Orf, and Colee all testified as torespondent's involving the children in disputes between theparties.

This court has recognized that joint custody cansucceed only where the parties have an ability to cooperateeffectively and consistently with each other toward the children's best interests. In re Marriage of Wycoff, 266 Ill. App.3d 408, 412, 639 N.E.2d 897, 901 (1994). While the agreement didnot provide for joint custody in Colorado, the agreed jointdecisionmaking would require similar cooperation. The recordshows that, in the past, respondent has not effectively andconsistently cooperated with petitioner on matters in the children's best interests. Thus, the feasibility of the agreement asto joint decisionmaking regarding the children's upbringing isdoubtful.

Last, the children are doing well in Decatur. Petitioner, petitioner's present wife, Nelson, Colee, Mikels, andTaylor testified that the minor children were involved in extracurricular activities and had friends in the neighborhood. Petitioner further testified the children have integrated intothe community. Nelson stated the children seemed quite happy.

Accordingly, the trial court's conclusion that remaining in Illinois was in the children's best interests is supportedby the record and thus not contrary to the manifest weight of theevidence.

For the reasons stated, we affirm the trial court'sjudgment.

Affirmed.

MYERSCOUGH, P.J., concurs.

STEIGMANN, J., specially concurs.

Although I agree with the majority opinion, I writespecially to provide additional clarification regarding respondent's argument that at the July 2002 hearing on the petition formodification, the trial court erred by admitting evidence ofevents that occurred prior to the November 2000 dissolutionjudgment. Specifically, respondent contends that the courtimproperly considered Dr. Scott's custody evaluation reportbecause that report was before the court prior to its November2000 order granting petitioner custody of the children. Thiscontention is wrong.

In November 2000, when the trial court granted petitioner custody of the children, the court acted pursuant to theparties' marital settlement agreement. Thus, the child-custodyissue was never litigated, and the court's role was essentiallylimited to accepting the parties' agreement with minimal, if any,scrutiny thereof.

In In re Marriage of Weaver, 228 Ill. App. 3d 609, 616,592 N.E.2d 643, 648 (1992), this court addressed a claim on anappeal from a custody modification proceeding that collateralestoppel applied, and we wrote the following:

"Collateral estoppel prevents a partyfrom raising an issue in a later proceedingwhere that issue was actually or necessarilydecided ***. ***

Generally, a court's order regardingchild custody is res judicata as to factswhich existed at the time the order was entered. *** Courts should be cautious indetermining when to apply res judicata inchild custody cases. This doctrine shouldnot be strictly applied to bar evidence whenthe most important consideration is the welfare of a child."

In In re Marriage of Kleiboeker, 262 Ill. App. 3d 644,634 N.E.2d 1329 (1994), the appellate court addressed a situationvery similar to the present case, in which the parties stipulatedto the petitioner's having custody at the time the dissolutionjudgment was entered in 1987. In 1992, when the respondentsought to modify custody, she presented evidence of petitioner'sinappropriate and violent behavior that occurred in 1986. Thetrial court granted respondent's petition to modify, and petitioner appealed, arguing, in part, that the court should not haveconsidered the evidence of his 1986 conduct. The appellate courtaffirmed, writing as follows:

"The court originally based the custodyaward to the father on the stipulation of theparties, without taking evidence as to thecircumstances of the parents or their abilityto take care of the children. Given thesecircumstances, section 610 [of the Act] allows the court to consider facts existing atthe time of the earlier decree but not thenknown to the court. [Citations.] We find noerror in the trial court's consideration offacts which were unknown to the court at thetime of entry of the previous custody orderin making its determination under section610." (Emphases added.) Kleiboeker, 262Ill. App. 3d at 649, 634 N.E.2d at 1332.

As in Kleiboeker, in this case, the Scott report wasessentially "unknown" to the trial court when it entered itsNovember 2000 custody order, pursuant to the marital settlementagreement. That is, although the report existed, it was notsomething the court considered when it approved the parties'marital settlement agreement. Once the child custody matter wasactually brought before the court, the Scott report (which wasmore than 40 pages long and contained information on the children's best interest) clearly became probative, and the courtproperly considered it. Indeed, under these circumstances andgiven the important task before the court, not only could thecourt consider the report, it would have committed error if ithad not done so.