Intercepting Comms

Is there a way using VB or VC to intercept a comms call nonintrusively (the app using the comms port continues to think it is using it) and redirect both send and recve internally to another program? I have 2 apps that normally would need 3 ports - only 2 available (laptop w/USB>serial) and the comms from the first app are consumed/responded to by the second app. Obviously there are better ways to do this but I have no access to the first programs source! If I can have app 2 intercept the send, process it and then post a "recve" back to the first as if it was a normal comms action I would ultimately only need one comm port (for yet anther reason).