serial port

I have a stop watch program which uses the same command button to start and stop.What I would like to do is attach a sensor to the serial port to activate this button.Or start and stop the timer directly.Does anyone have experience with this type of programming??? I know I need the mscomm control but then what??
What about a good electronics site that may help???
Please help I am going crazy

My best guess would be to use MSComm_OnComm event to listen to the port itself (or use the timer to periodically check if there is anythig there) and act to that accordingly.

Do a search on the forum for "MSComm". There are lots examples for this.