NO DUPLICATE VALUE IN THE COLUMN

P

Paulex

To all
Hello, Please help me about this.

I want a formula or validatation in 1 column that pop up a message if the
data is already available or already used.
 
T

Teethless mama

Data > Validation > Setting tab > Allow: Custom > Formula: =COUNTIF(A:A,A1)=1
 
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