Volume based internet restrictions

[Fletch <fletch_(_at_)_elecnet_(_dot_)_co_(_dot_)_nz>]

Greets

I am setting up an openbsd router to manage a companies intenet access, 
and would like to  deploy volume based internet usage.  I have setup 
squid, but it doesn't seem to have any options to limit a user by volume 
of traffic, only bandwidth.

Is there any solution to do this?  I pretty much want to limit volume to 
may 50mb a day per user and have it refresh each day.  I don;t care what 
they look at or how fast they get it, only that its no more that 50mb 
per day.

Or is there another solution or recommendation someone can make.

Thanks in advance for any help

Fletch

p.s. Have had no problems getting openbsd to run and think I'm gong to 
convert from Linux, as it just seems to be a hell of a lot better.  Keep 
up the good work.