I know this works, because of this question - How do I compare two Excel documents?
I have installed Newest WinMerge and http://freemind.s57.xrea.com/xdocdiffPlugin/en/index.html newest plugin(I copied the 2 fiels to WinMerge install dir and one to MergePlugins dir). But when I open two excel nothing happens and I see the ... compiled format and not excel.