Add a help column, if the invoices are in A2:A500, then in the help column
in row 2 put

=COUNTIF($A$2:$A$500,A2)=1

then copy down the formula as long as needed (in my example to row 500)


will return TRUE for those that occur once and FALSE if they occur more than
once
if you prefer TRUE for multiple occurrences change the =1 at the end of the
formula to 1



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Regards,

Peo Sjoblom


"workingwoman" wrote in message
...
I have an excel spreadsheet that I want to make sure that I do not have
duplicate invoice numbers. Can I accomplish that and how?
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Deborah Motte