title: How to perform multiple masks on demand on an Input field
body: <p>Iam trying to perform a mask on input using <a href="http://igorescobar.github.com/jQuery-Mask-Plugin/" rel="nofollow">jquery mask plugin</a>, What I need to do is to perform two different masks:</p>
  
  <p>US###-###-###-###-###-### this mask must be applied if the user is trying to type some numbers at first. (Which here I mean digit entry by #)</p>
  
  <p>but if the user decided not to type any numerical at first I want to let him enter any kind of letters or unicod character or numbers (totally any character) after that</p>
  
  <p>How should I perform such a mask?</p>