I think you're involved in a pyramid scheme. I have been duked by such models before, and the chances are you won't get any money at all. See netbux or freeipod. I can help you write a script, but I'd need to know how you are sent these invitations, and then it would be a simple matter of parsing out the url, higher languages like python have libraries for doing all this, so the hard part is pretty much done by the time you start programming.