When you need explicit control over data entered in a field, such as a range of numbers or dates, you can enforce a validation rule , which causes Access to test values a user enters in a field. If the value doesn't satisfy the validation rules criteria, Access refuses to enter the value and displays an error message. You can specify the text of the error message yourself. You can use the Expression Builder to create a validation rule by selecting the functions, constants, and operators you need for your rule from a list of options.
Create a Validation Rule
Specify Validation Text