[Serusers] Regarding Performance Counters

Hello friends I am looking for a way out to record as to how many INVITE messages have been processed, how many calls got in voice, how many remained in just signalling... for estimating/analysing the performance counters or traffic on the SER. I had posted this question earlier also, but dint get nething However, I just came thru the module AVP in SER, in which it says, we can store the attribute value pair.. adn can define our own attributes too.. Which gives me an idea to create a variable say.. invite_count, and everytime INVITE request is processed thru SER, I can increment it. However, A major doubt i have is that.. if i can perform mathematical operations on the AVP??? Can anyone help in this?? and Am i going right?? or something better exists?? Please help... Thanks! Parminder Nayyar