Separation Agreement Questions

In April 2012, my ex-wife and I signed a separation agreement and I filed for divorce, which became final in early June 2012. She has physical custody of the children. During mediation it was agreed that I would get them for three weeks (one in June, one in July, and one in August) each summer upon giving her 30 days notice. It seems that a mistake was made when the papers were drawn up because the papers say that she gets them for one week each month in the summer. We bothed signed them, as well as a judge. She now wants to change the agreement. Of course, I don’t want to. Can she just get it changed because she isn’t happy with it? If so, how? If it turns out that I do end up with the children for one week each month in the summer, does she get to decide which weeks? It was my understanding that I could get them any three weeks that I wanted, as long as I give the required 30 days notice. She says that I only get three weeks, regardless of the agreement (since it was a mistake) and that she has to agree to the 3 weeks.

If she wants to change the agreement, she can file a child custody claim and have the court decide it as a new issue. I cannot answer specifics about the agreement without reading it, nor can I tell you what the judge would order in the event that a new action is filed and heard.