You want to format a text field on a Business Object to display in the format of a US phone number: (___) ___-____
1) Go to Configure Application
2) Open the relevant Business Object
3) Go to the Form that the Field is displayed on
4) Click on the text Field to select it
5) On the left side, under Control Properties, change the Edit Mask to "US Phone."
This mask prevents letters from being entered into the text field, and also limits input to 10 digits.