Cookie Tracking Functionality for Rebates Website

Looking for someone to write software for a Rebates website that I want to create. The functionality should be similar to what can be seen on Ebates dot com . My website will have only one merchant and when a user clicks on the merchant's link, there should be a cookie that tracks their buying activity in the merchant's website and stores in a database and also on their individual profile. With this info, I should be able to process a payment for them through Paypal or other payment methods.. If you feel that I haven't explained properly, please look at other rebates websites for reference.