If you want to set private addressing 10.0.0.0 network for instance, assign another IP to the router , say 10.2.20.250
make this the primary route , with the original as secondary, make sure that the range is set up on both ends and allowed via the firewall. Next create the scope using remote route IP as default gateway for that scope .... roberts' your mothers brother as the saying goes.
what routers are you using ? I may be able to forward info on settings, we use 3com and cisco here


Steve