Say the values in "detail" are in Column A, from A1 to A100.

If you have your unique list of values in "summary", also in Column A,
Enter this in B1 of "summary", and copy down as needed:

=--(COUNTIF(detail!$A$1:$A$100,A1)1)

This will return a "1" if there are duplicates, and a 0 if there are 1 or no
matches.

--
HTH,

RD

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"Secret Squirrel" wrote in
message ...
I have a worksheet with a detail tab and a summary tab. In column A on my
summary tab I have a list of values. What I want to do is look these
values
up on my detail tab and see if they exist more than once. If they do I
just
want to return a value of "1" in column B on my summary tab. Some of these
values are a combination of text and numbers. How would I write this
formula?