The "Read From Spreadsheet File.vi" reads only text data, not from an Excel spreadsheet file (as the name might imply). You need to use Active X to invoke and read directly from a spreadsheet. It's not too tough if you've got examples.
Check out the following thread. It's got some examples:
http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=135&HOID=50650000000800000035480000&UCATEGORY_0=_49_%24_6_&UCATEGORY_S=0&USEARCHCONTEXT_QUESTION_0=read+from+excel&USEARCHCONTEXT_QUESTION_S=0
~Tim