With the exception of Value and Delete, data validation properties and methods cannot be used unless all of the represented cells currently have the same data validation criteria.

Use Value to determine whether the represented cells meet their data validation criteria.

Use Add to add data validation to cells which currently have no data validation.

Use Modify to modify data validation settings of cells which already have data validation.

Use Delete to delete all data validation criteria currently associated with the represented cells.

Use InputMessage and InputTitle to get and set the input message to be displayed when one of the represented cells is active.

Use ErrorMessage and ErrorTitle to get and set the error message to be displayed when data validation fails.

Reference