All NI-DAQ functions have their entry point in nidaq32.dll. Loading it will load the dependant dlls so, really, loading nidaq32.dll is all you need to worry about. Except for NIDAQErrorHandler(), like you said. The reason is because it isn't actually part of the NI-DAQ API. It and a couple other functions that start with "NIDAQ..." are just utility functions to help demonstrate the shipping examples. I believe that function needs nidex32.dll.
Russell
Applications Engineer
National Instruments
http://www.ni.com/support