153589 Referral System

I need a referral system for [login to view URL] What is needed is each user is provided a link, such as [login to view URL] They can share that link with their friends, family, and anyone on the net. The script records the number of people that follow that link and how many of them actually sign up. Or I would be happy if it just shows the number of sign ups through the system. If it would also be possible to have the script show the user the number of people he referred that would be great also. Please note, I already have a system set up to register users so this script would have to fit in with that. Thanks so much!