Sharing RS232 Comm Port between programs.

I am writing a program that will access COM2, make a call to a remote modem, and then attempt to handoff the modem connection to a separate application.

Is there any way to release the COMPort, with out hanging up the modem line? Or is there some way using threading to put the COMPort to sleep, and allow another application to capture it?

I appreciate any angles and ideas, thanks!

-Jared.