What is modification?
A modification is a change to a prior judgment.

Does this include separation agreements?
Yes.

But I thought that the agreement was a binding contract, now you say it can be modified?
Under certain circumstances, even a binding contract can be modified.

What circumstances?
Well, first look at your agreement (assuming you have one) and you might be able to tell if it can be modified. If you can't tell, call your old divorce lawyer and ask.

If there was no agreement, just a judgment, what is the legal standard necessary to modify the judgment?
You must show a "material change in circumstances, " generally unanticipated at the time of judgment and not caused by your intentional acts.

Then what?
Assuming you pass the "material change" test you can file a complaint for modification.

How can I file this "complaint"?
You complete a form filling in the particulars, such as, the section of the judgment you want to modify and the nature of your material change in circumstances, and serve the complaint along with a summons.

Are there any exceptions to the "material change" standard?
Yes, if you can show that the best interest of the child(ren) necessitates a change, then the judge will be more inclined to modify your judgment.

What will this cost?
It depends. Modification proceedings are sometimes simple and inexpensive and in other cases may be more complicated, contested and expensive than the original divorce.