USB is a device bus like PCI, so you would have to communicate in a device driver with kernel-level communication. CVI is not able to write device drivers (VXD files). You would need to use another compiler that has driver development capability like Visual C++ with the Driver development kit (DDK).
Another option would be to use NI-VISAs generic USB RAW communication capabilities. You can read about how to do this in the VISA Help under your Start menu under National Instruments->VISA->NI-VISA Help. In that help file, just seach for USB and you should find the information. You may need to update your VISA if you are using an older version.
Best Regards,
Chris Matthews
National Instruments
