Help Required - Repeating optional character in PatternMask

[amoghh]

I have a pattern mask which formats a US phone number - (000)000-0000
I want to add an optional repeating group of allowed characters after the current mask format for e.g (000)000-0000$
where $ can either not exist or can be any of [0-9] or comma or brackets in any repeating fashion. Basically i want the mask to function as kind of a validator prefix which validates the phone number format and after which any of the above characters can be typed after it. Can anyone help me to figure this out