Reroute a machine to another internal gateway (remote site )

i have a pc (ftp pc) that i would like to re-direct all internet traffic to that particular site internet connection, how do i go about doing this? . My site is A and the other site is B, we are both connected leaseline via cisco 2600 and i can ping servers, etc but i want to have this pc based at SITE A but use the default gateway of Site B,,,how do i do this,,,the SITE B is aware of this pc where PIX firewall has been told and i have tried by adding route add entries on this pc (ftp pc)