From The Document Foundation Wiki
- Validate this format by clicking the icon then OK
- Close the table
- Using the wizard create a form with the telephone field on it
- In design mode, click on the form navigator to access all the form controls.
- A right click on the telephone number field will allow you to check and complete the control properties.
- Exit design mode. The form is now ready to use for entering data.
- Enter the telephone number without spaces
- The formatting is applied when the cursor moves to the next field.