Comparing Excel Workbooks with Synkronizer
A free version of the Synkronizer add-in for Excel is available for download here. It can be used to detect differences in two Excel workbooks. The trial version only covers the range from A1:Z100.
As you can see in this example you can select individual worksheets to compare can specific cell ranges:
Synkronizer provides you with a list of the cells that have differences, and also highlights the different cells as well.