Explanation
Data validation rules are triggered when a user adds or changes a cell value.
The UPPER function changes text values to uppercase, and the EXACT function performs a case-sensitive comparison.
The AND function takes multiple arguments (logical conditions) and returns TRUE only when all arguments return TRUE.
The first logical condition compares the value input by the user to an uppercase version of the same value:
EXACT(C5,UPPER(C5)
The second logical condition tests that input to C5 is actually text
ISTEXT(C5)
If both conditions are TRUE, the AND function returns TRUE and input passes validation. If either condition is FALSE, AND returns FALSE and input fails data validation.
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
Explanation
Data validation rules are triggered when a user adds or changes a cell value.
This custom validation formula uses the WEEKDAY function to get a numeric value, 1-7, corresponding to a week beginning Monday (1) and ending Sunday (7). To get a number for a Monday-based week, the return_type argument for WEEKDAY is provided as 2.
The WEEKDAY result is then compared to 6. Any value less than 6 is a weekday, so the expression returns TRUE and validation succeeds. If the weekday number is not less than 6, validation fails because the date is a Saturday or Sunday.
Date is weekend
To allow only dates that occur on a weekend (Saturday or Sunday), you can use a similar formula:
=WEEKDAY(C5,2)>5
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
