I am looking to add a field constraint to a text field that will create a 'mask' for the users to input their phone number in the following format (###) ### - ####.  There is a constraint that 'masks' the numbers like ###-###-#### but my database format includes the parentheses.  I've tried adding this via regular expression, but I am having no luck.  Any idea how to get the parentheses in there?  

-Nate