Conversion Tracking Script Needed For Ecommerce Store

Our online store uses Interspire Shopping Cart. We have agreements with other companies in order to provide us with traffic from their websites. What we need is a script to log the leads from them that generate sales only. (we need to be able to sort this sales by lead in order to calculate a commission per each sale they drive us) How you go about doing this we leave up to you. At the end of the month we need to be able to see what sales resulted from these companies, and cut them a check. If we can perhaps have a GUI where we can view all sales, and be able to group sales by referrer or lead that would be great. We know that affiliate sites utilize a similar system, but we want to use a scrpt independently running on our system calculating this. Say for example [login to view URL] sends us 20 users in a week. 10 of those users result in sales. We arn't interested in the 20 users they sent us (we have awstats for that), we need to know those 10 sales they've sent us, group them, and calculate a commission based on entering a percentage for the sale prices of those items. So company 1, sends us 10 users, each buying 1 product at $10.00 each. Enter in % within web GUI, say for eg: 10% and throw them a $10 commission ($1.00 each item). If you can integrate this into interspire shopping cart, that would be perfect. If you have your own system which can utilize the conversion tracking feature of interspire shopping cart, that works great too. I have attached a screenshot, and parsing instructions somewhat listed in ISC. If you require any further elaboration, please feel free to contact us. We look forward to working with you, and successful completion of this project will result in your services being utilized for other tasks we have. We are reputable and you will be paid for your services. We are currently working on a budget, so the best skill/rate balance will be chosen. Thank you for checking out our listing, and we look forward to working with you!