Compare & Analyze Versions of a workbook with Spreadsheet Enquire - Standard part of Excel 2013 Pro editions

Compare versions of a workbook, analyze a workbook for problems or inconsistencies, or see links between workbooks or worksheets. If Microsoft Office Professional Plus 2013 is installed on your computer, chances are the Spreadsheet Inquire add-in is available in Excel.

Full Tutorial on Microsoft Site

for Older versions of Excel Spreadsheet Compare is the best free comparison Tool -