I recently needed to compare the results of two spreadsheets to check for differences between them. Although newer versions of Microsoft Excel have this functionality baked in, I was using a computer with Excel 2010 installed.
Thankfully, Svetlana Cheusheva at AbleBits wrote a blog post earlier this year that explored the different options for this sort of task. The approach I took involves having both spreadsheets in a single workbook, then inserting this in a third spreadsheet:
=IF(Sheet1!A1<> Sheet2!A1, "Sheet1:"&Sheet1!A1&" vs Sheet2:"&Sheet2!A1, "")
You then copy that formula from cell A1 to all the other cells where, in the first two spreadsheets, there might be data.