title: Customize ProgressView
body: <p>I'm trying to make a control that seems a customization of the progress view.
  This is what I should want to make. 
  It is a progress bar that would work as a countdown timer. Start at 30 seconds, and the bar is green. As the time progress the bar is shorten.
  When the time is 20 seconds the bar turns to yellow. At 10 seconds, the bar is red.</p>
  
  <p>Hope you can give me some idea how to customize it w/ the progress view? or is it of another control?</p>