Hello Chester,
If you are looking for an example program that uses the PeakDetector() function, please take a look at \samples\analysis\phasedif.prj. If you are looking for the source code to the PeakDetector() function, then I must advise you that we only provide our analysis library in compiled, object code form (analysis.lib). If you have any further questions, please feel free to contact us directly.
Jeremiah Cox
Applications Engineer
National Instruments
http://www.ni.com/ask