just to add a bit more info.  If I try 
status=dos(['.\dcmdjpeg ', FilNam1 FilNam2]);
then I get the error 
$dcmtk: dcmdjpeg v3.6.0 2011-01-06 $ 
dcmdjpeg: Decode JPEG-compressed DICOM file 
error: Missing parameter dcmfile-out 
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