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I'm sorry to hear about your situation.
If this provision of the custody decree was violated, that's called "contempt". The next step would be to file what's known as a "Motion for Order to Show Cause and for Contempt". That's essentially asking the court to tell the other party to explain why he/she violated a court order, and if there's no good reason, then it can hold the other party in contempt. Contempt could be a range of penalties, from monetary sanctions to loss of rights, even to jail time for noncompliance.
You should contact the court clerk and ask about the process to file a "Motion for Order to Show Cause and for Contempt", and what needs to be done next. Furthermore, if you get an attorney, you can ask for attorney's fees and costs as part of the sanctions.
That being said, you should contact an attorney in your area that deals with family law cases. Go to www.lawyers.com or www.legalmatch.com to find an attorney in your area. You should be able to find one that will give you a free initial consultation and better advise you of your rights, any problems with your case, likelihood of success, how courts are treating cases such as yours in your area, and what you should do next.
Use LawHelpCa.org to find legal aid offices, lawyer referral services, and other free and low-cost services in your county. You can also contact the Family Law Facilitator in your county to assist further in self help cases: http://www.courts.ca.gov/selfhelp-facilitators.htm
Hope that clears things up a bit. If you have any other questions, please let me know. If not, and you have not yet, please rate my answer AND press the "submit" button, if applicable.
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Thank you, ***** ***** luck to you!