Help with price recalculations

:blush: Hi everyone!

I have searched the whole internet to solve this problem maybe you can help. I have made a website with virtuemart as the shopping cart, need to enter into the php some code to help me but im clueless as what to write, heres my problem. I need something that will automatically calculate how much a product would cost over a time period set by me. An example would be a camera $400 total - $7.60 a week over 12 months, $15.30 a week over 6 months.
Do you have something like this I could use or adapt? Any ideas you could offer would be great!

I have always used Kirupa.com to solve problems so i hope you can help!