In the LiveCycle Designer, you can use a phone number field. To add the
Phone Number field and validation:Open your form in LiveCycle
Designer.Click Insert -> Custom-> Phone Number. You can choose UK or
North America In the field tab of the properties window, specify the Max
Chars for the phone number.Click patterns. In the validation tab, select
type and click apply.In the value tab, specify custom messages. You
should be able to add the validation. Let me know your thoughts.