Dan,
The lvdaq.dll was built to work with the DAQ VIs within LabVIEW. From LabWindows/CVI you will be interfacing with the nidaq32.dll. The header file, nidaq32ex.h, is the header file that the example programs use to interface with NI-DAQ.
There are several example programs that show how to interface with a DAQ device through LabWindows. If you installed NI-DAQ with support for LabWindows/CVI, then examples will be installed in the ...\Program Files\National Instruments\MeasurementStudio\CVI\samples\daq directory. All of the header files needed to interface with NI-DAQ are within the ...\Program Files\National Instruments\NI-DAQ\Include directory. I hope this helps.
Regards,
Todd D.