I'm in the process of getting a QDRO. I was awarded 50% of my ex husbands pension that is now payable. Can I put a lien on his portion for the $200,000 in arrears in support?

This is more a question for your lawyer as in general it is not normal to attatch those types of funds. You are already getting 1/2.

If your ex-husband is in violation of your divorce agreement to the tune of $200K your lawyer should be all over it. And I would have thought that the QDRO would have been put in place at the time of your divorce - what's the delay?