For example if the names are in column A then use conditional formatting, for
A1 use:

=COUNTIF($A:$A,A1)1

and set the format to bold.

Once entered, copy the format in A1 all the way down.
--
Gary''s Student


"Anna" wrote:

Hi
Does anyone know a formula that can find "doubles" in the list?
For example a list of thousands surnames. I want to check if theya re not
repeated..

Thank you in advance!