My Office Manager has a spreadhsheet containing last names, first names,
addresses, etc. As the spreadsheet gets longer, she worries about accidently
entering identical information (last and first names) without realizing it.
What I'd like to do is the following:

Put a Flag in Cell A1 which says: "Matches Found", and use conditional
formatting to turn any of the matches "red" (last name and first name) for
easy identification. If no matches occur, the flag in Cell A1 would say: "No
Matches Found".

If an identical match occurs in Column A or B

Jones, Paul B.
Doe, Leo
Jones, Paul B.

Of course I'd like the formula to be clear enough so a match is not
triggered when similar but not EXACT matches occur:

Jones, Paul B.
Jones, Mary C.
Doe, Leo T.
Smith, Frank L.
Smith, Mary

Any suggestions? I know she will be excited if I can give her this
information!

Dan