Per user data limits

Almost all of my users are connected through wireless WPA2 Enterprise. They authenticate to a RADIUS server and I would like to figure out a way to assign a monthly data limit on a per user basis. I would like to tie the MAC addresses used to login to the wireless in the Windows Server and then run a script on the mikrotik router to adjust the data cap on their ip.

If you can’t set those limits from the radius server then you’re probably using a crappy one.