BWANG,
I might suggest using the regular file I/O VIs if you want to change how the data is stored, rather than trying to change how the LabVIEW measurement file is created. An easy VI to use is the Write to Spreadsheet File VI. If you want a little more control I might suggest looking at the Write to Text File.vi (Help >> Find Examples, search for "File"). Hope this helps!
Andy F.
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National Instruments