Here is a thread that provides both a formula approach and VBA approach.
Compare two sheets in Excel
Another possibility is to get John Walkenbach's utility called
PUP [Power Utility Pak] (just released v. 6 this week).
J-Walk's site for PUP
If you buy one of his books, it comes with the book, otherwise $39 US. There several hundred speciality utilities that are all time savers - one of them is this very issue. If you don't know who Walkenbach is, then you need to know who he is - one of the premier Excel specialists in the world. His books include:
Excel Charts
Excel Formulas
Excel Power Programming with VBA
I have all three handy on my desk and use/refer to them daily. PUP is the best utility I have found for Excel (and I have several).
btw - I have no stake in J-Walk or his books/products. I am a satisfied customer.