Connecting to gateway on a different subnet?

I am trying to run a test system with very limited resources. I have an XP system running Windows Vista as a virtual machine. They are both part of a domain. I am trying to test a remote VPN connection through a secondary line we have and have setup the virtual machine with an IP address on a completely separate subnet, lets say 192.168.1.1, I am then trying to connect it to a gateway of 192.168.50.254. I can’t change the gateway IP and if I change the IP address of the virtual machine onto the same subnet as the gateway the test will be pointless as I will be on the same sub as the server i’m trying to connect to remotely (I think that makes sense:)).
Am i clutching at straws here or is there a better way?

Regards
Dean