I wish to write a program to measure DC offset value from a AC waveform by using NI PXI 4065.
The programming language i'm using is Visual C++.
I would like to know that is that any particular function or parameter is used for measuring DC offset?
Or i just use niDMM_Read() to read the measurement and use niDMM_FormatMeas() to measure and get the DC offset value?
No, there is not a specific function dedicated to measuring offset - your method of measuring the signal and comparing is correct.
According to the specifications [p6] for that DMM, if you are using analog functions AC coupling will automatically be enabled. This, of course, should elimiate your DC offset anyway.