PSP with partial refund option after some time

I am going to build a web site that will have few products, and a shopping cart. Every product will have an expiry or end time. Customers will buy any of the product(s) and after the product is expired, I need to gave back a discount of few bucks to all the customers(Partial Refund.) Now the question is which PSP(Payment service provider) I could use for this purpose.? I have came across Stripe (https://stripe.com/). Its a very good PSP. but they require me to store all the product information on their API and calculate prices on their own (which I dont want). All I need is to have the option of order and refund back after sometime. Any help would be highly appreciated. Thanks!

via Chebli Mohamed