How do you enforce court order for ex to pay medical bills on 4 kids dating from the year 2000?

My ex and I have been divorced since 2000. He is ordered by the court to either carry medical and dental insurance on our 4 children or pay 100% of their medical/dental bills. When he has the children covered by insurance he is required by the court to pay 50% of all out of pocket expenses. Since 2000, I have sent the bills via cert. mail and only 1 out of over 100 have been accepted. He lived out of state and then returned to Texas. For 4 years I was playing hit and miss with sending the mail to him because he moved so often. I have given him bills in person and had him sign for them. He has 10 days from the receipt to pay and refuses. In Oct.-Nov. the kids had over $2000 dental work done. He received the bills cert. mail 1 mth. ago. His wife says I was over charged and should take them to her dentist and that they will review the bill and decide on how and when to pay it. I told HIM I was willing to make a payment plan. He ignores me. Any suggestions, I live in Texas
--------------------
if you had checked all medical bills need to be presented to the friend of the court, attorney general's office in texas. there is a time limit you have to submit the bills. this is why most women don't get reimbursed. read the fine work and remember only the courts can enforce payment
Source