Many people don't consider the steps which need to be taken to enforce a violation of a divorce decree - and thus make mistakes in the process.
Set-up the default
Many settlement agreements have default notice provisions contained within them. In other words, if you wish to allege your ex-spouse violated the agreement, you must first send them an itemized notice of their violation(s). Most such default notice provisions require same to be sent via certified mail, return receipt requested, or via UPS/FEDEX. If you fail to do so, there's the possibility your violation application will be dismissed. Moreover, if you send the default notice, this sets up a counsel fee application even better, as then you can argue the other party had a chance to remedy the violation.
Be sure you're in "substantial compliance" yourself
Have the full agreement reviewed by your potential attorney, so s/he can go over with you whether you are in "substantial compliance" with each provision yourself. I have had many potential clients who wish to, for instance, sue for back child support, while they are violating one or more terms of the joint custody arrangement.