I want to create 30 day user and counting time after first login

ex. First login on May 11 2011 it will expire on June 10 2011, and other user which create on the same time not counting if not login

but I confuse about limitation and profile
Limitation menu have uptime
Profile menu have validity

I try fill 30d in uptime field and 30d in validity field it not work

Dear ,

If you use good idea , use radius server , this server Organization for great user and limit uptime and another rule you want to use ...