Is it possible to filter the text format of a TextField<String> in a manner that it would only allow Strings in the format 00:00:00:000 (hours : mins : secs : millis) so that the user could not enter more characters than allowed, only input integers, and couldn't replace those colons?

EDIT: Oh, and by filtering I mean in a way that the user could not input illegal characters at all, not the way the current Validator system works.