Forget about VB - just think of it as a serial comms problem: so you want to connect the serial port that your VB uses to another serial port attached to a hypoterminal.

If you have 2 serial ports on your PC, you can run both the VB and the hypoterminal on the same PC, and just link the serial ports with a cable.

If you have only 1 serial port on your PC, you will need to use another PC for the hypoterminal.

Either way, you will need a crossover cable.

Once you have got the VB working, I suggest that you replace the hypoterminal with a Keil simulator running your embedded code. Setup the simulator so that it uses the COM port for serial IO (see the Manual), and connect it just as for hypoterminal.
Then you can set breakpoints, single-step, etc, etc, etc,...

Then you can try it with your real hardware.