About creating input masks to control how data is entered in a field or control (MDB)

Microsoft Access provides two field properties that produce similar results: the Format property and the InputMask property.

Use the Format property to display data in a consistent format. For example, if you set the Format property for a Date/Time field to Medium Date format, all dates entered will display in this form: 12-Jan-1999. If a user of your database enters a date as 01/12/99 (or any other valid date format), Microsoft Access will convert the display to the Medium Date format when the record is saved.

The Format property affects only how a value is displayed, not how it is stored in the table. Also, a display format isn't applied until the data entered is saved— nothing is displayed in the field to suggest or control the format in which data is entered. If you want data to display exactly as entered, don't set the Format property. If you need to control how data is entered, use an input mask in addition to, or instead of, a data display format. An input mask ensures that the data will fit in the format you define, and you can specify the kind of values that can be entered.

If you define both a display format and an input mask for a field, Microsoft Access uses the input mask when you are adding or editing data, and the Format setting determines how the data is displayed when the record is saved. When using both Format and InputMask properties, be careful that their results don't conflict.