VLAN Based Monthly Traffic Counter

Hello,

I would like to implement a traffic counter, which would be vlan based. I could manually reset it every month, but I need it to just count in and out data transfer on a specified vlan.
I looked at traffic accounting, but that is too granular (per IP) and will not scale (max 8192 IP pairs) for this purpose, so I am guessing it is designed for something else.

Any suggestions on where I might look?

check these:
http://wiki.mikrotik.com/wiki/Automated_Usage_Script_without_usermanager
http://wiki.mikrotik.com/wiki/AutomatedBilling