HOWTO:Calc. a user-fee for cpu vp cpu-time

I have to monitor the system performance and turned on the 'acct'-system to see who is using all the cpu-time. It is the cpu-vp that uses most of the cpu-time. Is there a way to find out how much cpu-time a session (user) needed? I took a look at the administrator guide and the trusted facility guide but found nothing about this. Thanks, Erik