Explanation
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.
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, C5.
Data Validation Guide | Data Validation Formulas | Dependent Dropdown Lists
Related formulas
Data validation allow text only
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...
Data validation only dates between
Data validation rules are triggered when a user adds or changes a cell value. The AND function takes multiple arguments (logicals) and returns TRUE only when all arguments return TRUE. The DATE function creates a proper Excel date with given year, month, and day values. Because we want to allow...
Related functions
ISNUMBER Function
The Excel ISNUMBER function returns TRUE when a cell contains a number, and FALSE if not. You can use ISNUMBER to check that a cell contains a numeric value, or that the result of another function is a number.
