Take a look he

http://cpearson.com/excel/duplicat.htm

In article <55b20bbda952a@uwe, "XYZ via OfficeKB.com" <u14790@uwe
wrote:

I need a help with formula to detect duplicate invoices (payments) listed in
my column I2 through I8317. In a separate column (next to it) I want the
computer to return information either by indicating "duplicate" or giving me
number of counts for particular invoice. The formula I tried was:
=COUNTIF(Invoice Number!$I$2:$I$8317,)I2

but it doesn't work and shows value error.

Tx.