Limit time online per user

Hi again,
I hope someone can suggest me a tip to do what I need...
I have NoCatAuth gateway and server installed on two 
machines. Authentication works on RADIUS that queries a 
PostgreSQL database. I used a SQL script that I downloaded 
at:

http://www.peternixon.net/tmp/dialupadmin-pg-netsnmp.tar.bz

and everything works fine.

I want to use DialupAdmin to manage users. It also seems 
to work fine, but I want to know I can limit time online 
per user, for example, how can I set that an user can stay 
online only 2 hours. I would like that after 2 hours his 
session expire and he can't stay online no more. I tried 
to set Session Timeout when I create a new user, but it 
doesn't work. Anyone can tell me where I can set this 
limit?

Thankssssss ;-)

Monica