What kind of device is your USB?
Does the device vendor provide any device driver and DLL module for the device?
The above link that Wim S provided is an approach that uses NI-VISA's USB RAW resource. It assumes that the device has BULK-OUT and BULK-IN endpoints but no need for vendor's driver. NI-VISA USB RAW hosts the device instead.
If the device vendor provides the device driver and DLL, you can use them through the DLL's function interface directly.
