This property is used to provide a filter to limit the characters that the user can input in a Combo-Box with the Drop-Down style. This property doesn’t have effect on Combo-Boxes with the Drop-List style.

The value of this property is a regular expression. Only characters that match the regular expression will appear in the Combo-Box when the user types or pastes them.

 

Example - Create a combo-box that accepts only letters and numbers (no grave letters or special characters allowed)