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Excel Data validation unique values only

Reject duplicate data entry in a cell range.

To allow only unique values in a given range, you can use data validation with a custom formula based on the COUNTIF function.



Note: Cell references in data validation formulas are relative to the upper left cell in the range selected when the validation rule is defined, in this case B5.

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In the example shown, the data validation applied to C5:C9 is:


where emails is the named range C5:C9.

How this formula works

Data validation rules are triggered when a user adds or changes a cell value. In this example, we are using a formula that checks that the input doesn’t already exist in the named range “emails”:


COUNTIF returns a count of the value in C5 inside the named range emails (C5:C9). 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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