Validators In A CellStep to reproduceInput Column
11. RequiredFieldValidator
2. RegularExpressionValidator
3. RangeValidator
1. Clear value then enter.
2. Input a character that is not a digit letter then enter.
3. Input a number that is out of range of [0, 9] then enter.
4. Input a digit-letter then enter.

You can use cell validators to specify what a user is allowed to type in a cell. You can also display an error message if the user types invalid characters.