Hi, I've searched previous posts as I know I saw the answer but can't find
it now and forgot to print it last time.

I'm inputting a number of part numbers (600 of them) in column A and need to
identify duplicates
as I enter them (on the fly).
Conditional formatting?

What I'd like is if I input a previously entered part number, any and all
occurrences of previous entries
of that part number to highlight so I stop double entries.

Please, not a macro as I'm not into macros yet.

I'm using Excel 2010 and also need the solution to also work on my other
machine using the 2007 version.

TIA.