Hi SoLost,
This is entirely dependant on the drivers for your DAQ device. LabJack most likely has a LabVIEW driver provided so that you can access your device within LabVIEW, but this would be entirely developed by them. The driver may come with some kind of documentation to help you learn the API, but any questions on how to use these drivers would probably need to be directed to LabJack directly. The driver should have some function to set the frequency, but this is independant of our software.
Thaison V