Control over Min announcements A2billing

I have a working production system, I need to factor an additional field in the callplan to control the min announcements. Example Callplan A- factor is 1 Callplan B- factor is 2 if mins available in both are 100, Customer on Callplan A should hear 100 mins available, where a customer with Callplan B would hear 200 mins available. The factor needs to multiply the available mins if the min announce is on in the AGI. Although simple Please ensure you know the AGI and integral part of A2billing to bid for this project.