Discount Difference payment

[Elevenbravo90]

I was wondering if there was an extension that took the default price and calculated the difference between default and discount prices then calculated the difference into monthly payments, for example.
Default price is 100.00, the discount rate is 70% so the discount price is 30.00. .... 100.00-30.00 = 70.00 that 70 dollars is added to a database that adds up per purchase up to 500.00 At the end of the month the user is required to pay 10% of the difference. for example they have a 70.00 difference from that oe purchase. they have to pay 7.00 or 10%. the amount they pay is then subtracted from their balance making the new balance 62.00