Accounting - limits

[Evgeny Yurchenko]

>Rizky Marunda Dinata
>Mon, 25 Jul 2011 06:34:04 -0700
>
>Dear Evgeny,
>
>Yes, freeradius is able to monitor and limit usage, for example will reject
>login after 1 GB of  sum ( download+upload), please read info about
>sql-counter (http://wiki.freeradius.org/Rlm_sqlcounter)

Thank you very much Rizky for your hint!
I've figured out how to use rlm_counter for the same purpose but I can restrict only based on Acct-Input-Octets or on Acct-Output-Octets.
Is there a way using rlm_counter to sum up these counters to make a decision on reaching limit?
Evgeny.