Define validation rules to control when a record can be saved

1. Open a table in Design view.
   
   
2. Click Properties on the toolbar to display the table's property sheet.
   
   
3. In the ValidationRule property box, type the validation rule. Or click the Build button to create the validation rule using the Expression Builder.

   For example, you could define the validation expression "[RequiredDate]<=[OrderDate]+30" to make sure that the date entered into the RequiredDate field is within 30 days of the date in the OrderDate field.

4. In the ValidationText property box, type the message that you want Microsoft Access to display when the rule is broken.

   For example, for the validation expression "[RequiredDate]<=[OrderDate]+30," you could enter "The required date must be within 30 days of the order date."

   If you set a validation rule in a table that contains data, Microsoft Access will ask if you want to apply the new rule to existing data when you save the table.

Notes

• You can specify only one validation expression for a table. However, if you want to specify more than one rule, you can combine expressions for the ValidationRule property setting with the And operator.
  
  
• Record validation rules are enforced whenever you add or edit data, whether it is through table Datasheet view, a form bound to the table, an append query, an update query, Visual Basic for Applications code, or by importing data from another table.
  
  
• You can test to see if the data in a table meets validation rules by right-clicking the title bar of table Design view, and then by clicking Test Validation Rules.