How to make a persistent counter?

[Kenneth Marshall]

Dear FreeRADIUS users:

I am trying to implement some load balancing for our
wireless network. Each user needs to be placed in a different
VLAN to distribute the use of each one. If I had a persistent
counter that I could access, I could use the rlm_expr module
to take the modulus of the counter and use that to generate the
next candidate VLAN. Does anyone have any idea about how that
could be accomplished?

Ken