Excel’s data validation is far more powerful than just dropdowns — here’s what it can actually enforce
https://www.makeuseof.com/excels-data-validation-more-powerful-than-just-dropdowns/
- Custom formulas let you control far more than a list
The Custom option accepts any TRUE/FALSE formula as a validation rule - Prevent duplicate entries with a COUNTIF formula
It flags repeats before they cause problems - Force entries to follow a specific pattern or length
LEN and LEFT keep the data consistent - Restrict dates so no one enters anything in the past
TODAY() keeps your date entries forward-looking - These rules get stronger when you combine them
Stack multiple conditions for tighter control