VPN proxy solution for 3G network

We need to achieve following goal: The mother machine(windows 7 Ultimate,x64) is connect to a fixed cable network, so the mother machine has a public IP. We need to create VPS(using windows virtual pc, the OS of the VPS is optional) in the mother machine, each VPS is connected with a USB 3G network card. Due to restriction of the 3G network, we are not able to setup VPN network directly in 3G network. So what we need to do is, we need the people dial in to the VPS by the public IP the host machine have, then connect to the internet using the 3G network. We need step-by-step instruction written in .doc so we can do this our-self. ps. there is also an option that put a router in front of the mother machine. linksystem E2000.