An application called I/O Trace should have been installed along NI-DMM in your system. It will trace all calls made to the NI-DMM (and other) APIs. A good tip is to use this to see how the Soft Front Panel configures the device as you use it.
Also, you should check out InstrumentStudio if you haven't yet, a modern replacement for the NI-DMM Soft Front Panel.
Chief Software Engineer
NI Driver Software