Identifying duplicate data

[KKD]

I have rows of data that contain a column with an invoice number, if I am
entering a duplicate invoice number, I want to be alerted. I want to be
allowed to enter duplicates, but I want Excel to somehow alert me that it is
a duplicate so I can check it. What is a good way to do this?

 

[Gord Dibben]

For alert only you could use Conditional Formatting to highlight duplicated
numbers.

Both instances will be highlighted.

In Format>CF>Formula is: =COUNTIF($A$1:$A$50,A1)<>1

Format to a color and OK

If you wanted to PREVENT duplicates you would enter this formula in Data
Validation>Allow>Custom

=COUNTIF($A$1:$A$50,A1)=1


Gord Dibben MS Excel MVP

 

[Max]

One easy monitor/alert is to use a formula in an an adjacent col
Assume you are entering data in A2 down
Put in B2: =IF(COUNTIF(A$2:A2,A2)>1,"<<Dup !","")
Copy down to cover the max expected extent of data in col A
Col B will give you the necessary visual alerts

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Max
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