Yes, they can take it. If you win the Lotto, they'll take that too. Just pay what you owe and then you won't have to worry about it anymore. If you believe that you are paying more than you are legally obligated, then you should hire a family law attorney and have him file a petition for modification of terms.
THESE COMMENTS ARE NOT LEGAL ADVICE. They are provided for informational purposes only. Actual legal advice can only be provided after consultation by an attorney licensed in your jurisdiction. Answering this question does not create an attorney-client relationship or otherwise require further consultation.