Welcome to WebmasterWorld Guest from 188.8.131.52
I believe nick patrick is trying to have the requests to a third party server look like they are coming from the user who initiated the request to his server?
If that is the case, the answer is "it's not possible." Even if you spoof the IP address, that would just mean your server wouldn't receive the response. On the internet, the IP you send is the IP which receives the reply.