Validation rules you assign to a column in the Database painter are used by default when you place the column in a form. You can override the validation rule in the Form painter by defining an ad hoc rule for one specific column.
To specify a validation rule for a column in the
Form painter:
In the Form painter, select Properties from the column's pop-up menu, then select the Validation tab in the Properties view.
Create or modify the validation expression, as described next. To help you work on the expression, you can use the button to the right of the Validation expression box to display the Modify Expression dialog box.
(Optional) Enter a string or string expression to customize the validation error message.
For more information, see “Customizing the error message”.
