A Complaint for Modification is the action by which you can request that the Court make a change to past Court Judgments. If the Orders that you want changed are only Temporary Orders then you must request a change by Motion.
A Complaint for Modification is the beginning of a new action and should only be used to change permanent orders which are called Judgments. To succeed on a Complaint for Modification you must prove two things: first you must prove that there has been a "significant material change in circumstances;" and second you must prove that the change in circumstances warrants a change in the Court's Order.
A "significant material change in circumstances" is a change in your life that is big enough to have an effect on the factors that related to the original Order of the Court. For example, if the Order that you want to change is a Child Support Order, then you must demonstrate that there has been a change to the factors that affect a Child Support determination, such as the income of the parties, expenses of the parties or needs of the children. In addition, you must demonstrate that that change is significant. In Child Support cases a good rule of thumb for determining significance is whether or not the change in circumstances would result in a 20% change in the Child Support Order.