Sorry for short words/ typos - on pda on-site

I posted regarding extending the function of the captive portal. But things got offtopic

I've setup a radius server - do deal with the requests, however, Nomater what strings I put in the
radius users file, I can't limit access time on an individual basis. I'd like to be able to limit
some to 30 mins, others to an hour, etc.

They do authenticate, just don't expire :-(

Any ideas? Even the most basic (i can be dumb and forget)