routing issuse

I was wondering if any knows how to set up port forwarding for more then one computer in witch the Application that running on more then one computer only runs off one port.

Example
Router A has ports for guild wars forwarded to PC X but not PC Y and PC Z
PC Y and PC Z get lag while playing guild wars but PC X does not.

If Router A has no ports for guild wars forwarded and PC X, Y and Z all get lag

The Router we are using is I would guess older router and only has the options to store up 10 ports forward. This one will allow me to enter the same port to be forward to more then one ipaddress. I noticed on some newer routers you can not even do this they limit the port to be forwarded to only one IP.

I know some applications Like Bit Tornado has a range of ports that can be picked and you can forward from in that range to same number of pcs as ports

Example program has range 12345 -12349
Pc x can use port 12345
Pc y can use port 12346
Pc z can use port 12347
None of these would get any lag because the ports are being forward strait to the computer it assigned and they are all running the same application.

I know Bandwidth is not the issues because if I set upforwarding to two machines the 3rd would lags and the others do not.

What should I do to try and get guild wars to stop lagging on the 3rd machine? Note the 3rd machine lags even if the other two are not even powered on.

I am limited to 10 slots and 6 are used by team speak and other apps.