GPO to block nework resources on server

I am trying to create a server environment where my software developer can log on to it through RDP on my development server and work on it, but I don?t want them to access my network from that server as I want to secure my source code.

I have windows 2003 installed on my development server.
It?s a part of my windows 2003 domain.

I want to create a GPO specific to my development server.

Please help with a GPO setting where I can block my network access from my development server.