Roaming hotspot users and radius

I have been trying to figure this out for some time now, and hopefully sombody may be able to help.
How do you track a users login time and bytes in/out when they roam between hotspots when using radius to authenticate them?
I am using freeradius, MT, and hotspot feature in MT. I can’t understand how to track users usage, then next time they login to MT hotspot, tell MT hotspot how much time the user has left, for example.

Anyone ?

Thanks Paul

Radius Accounting will send this information to your database. Enable it and check out your radius database.

I can get the accounting working fine, but what I can’t figure out is how do I use the accounting information that the AP sends back to the radius server to modify the user attributes and reduce the uptime and/or usage left for the user ?
For example:
User1 logs on and gets radius attributes saying that they have 60mins uptime and 10mb download.
They start a session and use 10mins uptime and 1mb or data then logout.
How do I tell the AP next time they login that they only have 50mins uptime left and 9mb of download left ?

Paul

Also, I am using a user file for user attributes and standard radius accounting log on my radius server (Freeradius)