DMZ Isolation using Proxy Server.

My company wants to have a lab environment isolated from the company’s VPN. When testing our VPN application, we want to be able to connent to the company’s VPN by switching the hub manually, then switch back when done testing. Can a proxy server do this with two cards instead of switching it manually with a hub? One card would be connected to the company’s VPN, another to the DMZ (development lab). This way we are not dependant on the network group to do this for us. Is this a lot of work? Can we also put a third card in the Proxy Server and create our own VPN – one card intranet, one card DMZ, and one card VPN?