I get a message when I attempt to enter data in Page view.

When you try to move out of a field after changing data, Microsoft Access validates the data, making sure that the value you entered is allowed in that field. If the value isn't allowed, Access alerts you. In order to move off the field, you must either change the data to an acceptable value or undo your changes.

A value might not be allowed in a field for the following reasons:

• The value isn't compatible with the field's data type. If you enter a value that doesn't match the data type, Access attempts to convert the entry to the correct data type. However, some data can't be converted to other data types. For example, you can't store a name in a field with the Number data type in a Microsoft Access database or the smallint data type in a Microsoft Access project.
• The data breaks a rule set in the ValidationRule property for the field.
• Data is required in the field, and you've tried to leave it blank.
• The validation macro specified for the BeforeUpdate property canceled the update.

Access also validates data when you move out of a record. Before it saves a record, Access makes sure that your changes don't break any validation rules set in the ValidationRule property for the record. Additionally, if the table you are editing has a primary key or unique index, Access makes sure that the record you are editing doesn't have the same value for the fields as another record in the table. If the record can't be saved, you must either make any necessary corrections, or cancel your changes by clicking Undo or pressing ESC.