title: formatting textfield while user is typing
body: <p>I would like the user to type an amount in a textfield and I want the value to be formatted as it is being typed. Which means as the user types in the 4th digit, a comma appears at the appropriate spot denoting the thousands. example: 3,450</p>
  
  <p>Right now,I am trying to use the textfield delegate method "shouldChangeCharactersInRange" and NSNumberFormatter. Unfortunately I haven't had any success. Could someone point me in the right direction? thank you!</p>