Create simple affiliate program

I need a simple affiliate tracking script created. All I need is to give different affiliates their unique tracking link, and then when the visitor fills out a form I get notified of who sent them to me. I don't need affiliates to be able to login to a special area or sign up, etc. I just need something really simple so when someone fills in a form on my website... I know what affiliate sent that lead to me. ## Deliverables This will need to work on at least two websites that I own (as affiliates can send to either one).