Affilate Marketing Purchase Script Tracker Development

I have a website, that serves as an advertiser with many affiliate marketing links. I need a programming script that will tell me when a customer who has registered into my website has made a purchase from any of the merchants on my site. I need this script, because people making purchases from my site receive cash back from me. I need a way of accurately determining who made a purchase, from where, the item(s), and the total amount of the purchase.
Currently, my site assigns an ID number to each registrant. That ID number needs to automatically insert into the Linkshare (my affiliate marketing company) software. How the ID number needs to work with the Linkshare software is included in the attached document. Please read the document before applying. Also, Linkshare has people familiar with the scripting requirement and they will gladly assist a programmer to build an appropriate script. Because of that, I need someone who can place a US phone call and discuss the scripting issue with Linkshare in English. Experience with the Sitebuilder software used by Hostgator would be beneficial.