Add functions to existing payment gateway

General information for the business: We sell subscriptions to web based scheduling software
Description of requirements/functionality: I have a php/mysql based scheduling software program and recently had PayPal PayFlow Pro integrated for the recurring billing cycles. It is currently setup with a 30 cycle for billing. When one of my users attempts to login, the software checks to make sure their account is current, if not, it gives a popup to make payment.

Right now, the payments in the popup are a set value, I.E. $45 per month for example.

My software is actually much more dynamic than that. Each of my users can have a different amount set for monthly billing, and they can have additional users in their accounts, which I can set any amount for as well. At the end of each month the third box in my billing report page totals the amount due for each client based on usage.

PayPal PayFlow Pro currently updates my database after a payment is received and it is based on a 30 day cycle from the time of initial payment. I am looking for someone who can add code to have PayPal access the "Total" due amount on the 1st of each month when a client attempts login and instead of showing a set amount, actually display the amount due based on usage, again, which could be different each month, for each client.

I would also like the Auto-Renew feature to be added so my clients can set that up and only be notified when a charge does not go through. My software has a Billing Profile page in each clients Admin Suite which can be altered to give them easy access for viewing their account details like, Subscription Status, Days Remaining, Auto-Renew On/Off, etc.

Please let me know if this interests you.

Thank you, Richard Renk
Extra notes: