When you and your spouse divorced, you may have had to come to an agreement on child custody. Both of you might not have been entirely happy with it, but that's not unusual. None of us wants to lessen the time spent with children we're used to seeing on a daily basis.

When situations change, so can your custody arrangement. Consider the factors that went into the original agreement: Your work schedules, who the primary caregiver was, and, if your child was old enough at the time, whom he or she preferred to live with. Many things can change over the course of raising a child. Perhaps you and/or your ex remarried, or maybe one of you moved to another state. Problems such as alcohol or drug addiction may have come up. If the changes are substantial, you may want to consider a child custody modification.

How does a modification work? It depends on the circumstances. If you and your ex agree on the change to be made, you can file a joint motion to modify custody and present your agreed order to the court, which will usually put it in place. If you don't agree, there must have been a substantial change in circumstances, one that has a significant effect on the life of your child. It must also be material, meaning it affects his or her well-being. The change must also be permanent to be considered.

Some changes warrant an evaluation, such as in the case of addiction or another problem that puts a child at risk. In that case, you may be able to arrange for a psychological evaluation of the parent, child and/or other family members to find the best living situation.

Sometimes instead of modification, you need enforcement if your ex isn't following a court order. In the end, remember that no child custody agreement is set in stone. An experienced family law attorney can help you fight for what's best for the changing needs of your child, whether it's modification or enforcement.

Source: Edmond Sun, "Ask A Lawyer: How to change child custody arrangements," Matt Hopkins, Jan. 27, 2012