Always include complete details in your question. Based on your question & comments, I found this from Google.
VISUAL BASIC COMMUNICATIONS #1 - how to take control of the serial port with VB6[
^]
Again I suggest you not to go with VB6, it's old, dead.
Here someone recently wrote an article on Serial ports using .NET.
Serial Comms in C# for Beginners[
^]
And finally, use Google for more things(But don't expect much on things like VB6, IE6, etc.,)