Can I remote two TightVNS servers that are behind the same cable modem?

[-=>Danny<=-]

I just set up TightVNC server on a machine that is behind a cable modem. I gave the machine a static IP address and set the port forwarding on the modem.
Everything works!
Now I'm wanting to add a second machine behind the same modem and I would like to be able to remotely control it as well. 
Since TightVNC uses the modem's IP address to connect to the machine that is already there, will I be able to control both PCs (not at the same time) with the local viewer?
If so; how do I set it up or where can I find documentation re how to do it?

Thanks in advance,

-=>Danny<=-