Conditional Formatting
a) all version of Excel;
Select the column of numbers (I will assume this is column A) and open the
Conditional Formatting dialog. The formula you want to use is
=COUNTIF(A:A,A1)1 and give a suitable format (light red fill, for example)
b) in Excel 2007: select the column of data, open the Conditional Formatting
dialog and locate "Format unique/duplicate..." and proceed from there.
best wishes
--
Bernard Liengme
Microsoft Excel MVP
http://people.stfx.ca/bliengme

"Jeremy" wrote in message
...
Is there a way I can write a script or conditional format to identify
duplicate data. The data can be marked by highlight if need be.

Ex
Since A1 and A3 are both the same numbers both locations become
highlighted.
I have a large range of data to perform this in. The numbers being
identified are lager than 2 digits.
A
1 12
2 13
3 12


Thank you