This program will do sort of what you want, it will list all the ports that have been opened by upnp enabled applications and allow you to add/remove ports.

http://www.codeproject.com/internet/PortForward.asp

What might be more useful though is you can download the source code so someone could easy make an application where you push a button to open the ports jj2 needs and another to close them.

Nice idea for a program! I’m sure quite a few people would find that useful.