You can define validation rules for table fields and for controls on forms.
To add validation rules to a form, you open the form in Layout view and add rules to the properties of individual controls.
Tip: If you create a form automatically from a table by using one of the Form commands on the ribbon, any validation for fields in the underlying table are inherited by the corresponding controls on the form.
A control can have a different validation rule from the table field to which the control is bound.
For example, suppose you apply the following rule to a date field in a table: Forces users to enter values in the field.
This is the same as setting the Required field property to Yes.
The steps in the section Add a validation rule to a table explain how to add validation rules to table fields.