iTunes Music Restriction

I have policy setup and configured in my environment and it already restricts some aspects of iTunes. My question is: I want to restrict the amount of music users can add to iTunes, without restricting the use of the app itself. My users need to use iTunes for their jobs and need to have some music in it, but I have found that some of them are loading their entire personal libraries into iTunes. I noticed an option in the plist for restricting the number of Movies and such (default is set to 300) and I was wondering if there is a similar preference option for music that I can set. I didn't see it in the existing plist options. All of my users are either 10.5 or 10.6, but most have been upgraded to 10.6. My Xserve is also running 10.6 server and is connected to Active Directory with schema extensions already in place.

Thanks,
Tim