There isn't an Excel function to compare the content of two websites to each other. In fact, I'm not aware of any free application that does this. I did come across a few paid applications like this one:
http://www.sobolsoft.com/comparehtml/[
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It sounds as though you have three options. One, you can do the comparison using a tool like the one above. It won't be quick because you cannot automate the comparison (that I know of) so that it runs down your list. Two, you could write a comparison engine yourself. Basically, create an application that downloads the entire landing page of the site. Either create a hash of the site's value (to compare if two are completely equal) or do a difference comparison using something like BeyondCompare (they have command-line options). Finally, your third option would be to re-evaluate your requirements. Figure out what the end result needs to be and either identify if that is really a good idea or figure out that maybe you can't do what you really want to do.