hi rannie,
You could send a text string from the PC to PIC as 'milan' suggests, but the method I have used is to label the GUI buttons in VB in a way that the user can understand and then transmit a 'control' character to the PIC when the user presses the command button.
eg:
Button label: 'Set Blink ON', when pressed sends say, hex code 01 followed by CR LF,,,the PIC echo's the string back to the PC.
On receiving the echoed string, VB changes the label to: 'Set Blink OFF'.
The PIC program decodes the hex 0x01 as a Blink ON command.
If 'Set Blink OFF' is pressed, send say, hex code 02 followed by CRLF.
E