Jacky,
This is a somewhat extensive topic, so my advice would be to go to the CVI help, then expand "Using LabWindows/CVI>>Instrument Drivers>>Building Instrument Drivers>>Creating a Function Tree".
Read the handful of topics below this node, and then see if things become more clear. If you still have specific questions after you've read those, feel free to post them year, and we'll be happy to answer them.
Luis
