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Data validation unique values only

To allow only unique values in a given range, you can use data validation with a custom formula based on the COUNTIF function. In the example shown, the data validation applied to C5:C9 is: =COUNTIF(emails,C5)

April 14, 2025 · 1 min · 44 words · Darius Morris

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Explanation

Data validation rules are triggered when a user adds or changes a cell value.

If the count is less than 2, the expression returns TRUE and validation succeeds.

If not, the expression returns FALSE and validation fails.

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Excel COUNTIF function

Explanation#

Explanation