using ethernet devices on 3g network

I usually run my netgear router into my airport extreme built into my time capsule, but as i have problems with my home broadband, i am now using 3g through my mobile phone. I can connect the airport extreme to the network, by telling it to join wireless network, which gives me access to the net and to the time capsule for time machine backups, and the usb drive plugged into time capsule, the only things that i dont have access to is the NAS which is plugged into the ethernet on the base station. Has anyone actually managed to do this and if so can you give me anypointers to setting it up.