ipfw and temporary port access

[Noah]

Hi there,

I am trying to figure out how to open a port temporarily for a specific 
IP who is able to provide a proper username and password on the website 
of the box.  After authentication is verified then the IP address is 
cached and temporarily allowed to access a specific port on the 
server.   This temporary firewall changes would be handled by ipfw.

Any clues if a system like this is a already coded and out there somewhere?

Cheers,

Noah