If it doesn't cause you any problem to merge them then this would be an easy way to eliminated duplicates. There are numerous postings on this message board explaining how to remove duplicates from a single worksheet. Also, Chip Pearson's site does a very good job of giving some ways of doing this, as in this example:
But if you want to keep the three workbooks or sheets separate then a VBA macro is the way to go. It would not be difficult to write such a macro (probably less than 20 lines of code).