I'm sorry but I don't know how to interface it by USB directly, however, you may want to search for a "virtual serial port driver" for your USB. The driver will trick your application into believing your USB port is a serial port and behave like one. The driver should handle the in-betweens of serial information exchange of the USB port and your VB program.

Again, I've never done this, its just a suggestion, the easier route would be to buy an actual serial data cable, but if you cannot, then maybe a USB to serial converter cable.

Here's a link to help you with basicsetup of serial communication with VB: http://www.pages.drexel.edu/~bns23/tutorial.html

Good luck.