Kevs, could you be a bit more specific with what it is you're trying to accomplish?
For example, do you want to compare two copies/versions of the same file to see what's different between them? Or do you have two different lists of data, for example customer contacts, and want to compare them to see which customers only appear on one or the other lists?
Excel is a wonderful, powerful program. However, it doesn't offer an easy way to compare two lists and highlight what's different. There are a couple of roundabout ways you can accomplish this in Excel, if this is what you're trying to do. (My experience with Excel is all in Windows, but I assume the techniques will work in OSX as well.) Any approach is going to be too lengthy to discuss here, especially since there are Web sites devoted to Excel that cover such topics in much detail. Best bet is to search the Excel Questions forum on MrExcel (
http://www.mrexcel.com/board2/). Search using the terms "compare" and "list" to start, you'll get all kinds of hits. I just saw a new post from yesterday that may help me accomplish exactly what I've been trying to do along these lines myself.
Hope this helps! Comparing two lists is a surprisingly tricky task to accomplish in Excel. If what you're really trying to accomplish is comparing two files, I'll have to defer to others for a possible solution.
Gary