Problem about simultaneous-use parameter and windows DC.

Hello guys. We set up a freeradius server several months ago. We use postgresql database for Users and Clients databases, and all works fine. Then we want to use a windows domain controller to do the anthentication by calling ntlm_auth. After some tests, it works too. But now we have no idea how to enable the simultaneous-use parameter, because tables of Users database is actually empty, all user informations are in the windows DC. Is there any way to enable the simultaneous-use parameter? Thanks! Miles