Explanation
Data validation rules are triggered when a user adds or changes a cell value. Cell references in data validation formulas are relative to the upper left cell in the range selected when the validation rule is defined.
The ISTEXT function returns TRUE when a value is text and FALSE if not. As a result, all text input will pass validation, but numbers and formulas will fail validation.
Related formulas
Data validation allow numbers only
Data validation rules are triggered when a user adds or changes a cell value. The ISNUMBER function returns TRUE when a value is numeric and FALSE if not. As a result, all numeric input will pass validation. Be aware that numeric input includes dates and times, whole numbers, and decimal values...
Related functions
ISTEXT Function
The Excel ISTEXT function returns TRUE when a cell contains a text value, and FALSE if the cell contains any other value. You can use the ISTEXT function to check if a cell contains a text value, or a numeric value entered as text.
