title: WP7 progressBar with gradient foreground behavior
body: <p>I was thinking how to explain this. Better with a image:</p>
  
  <p><a href="http://www.foxandxss.net/stuff/progressBar.png" rel="nofollow noreferrer">http://www.foxandxss.net/stuff/progressBar.png</a></p>
  
  <p>I want a progressBar with that gradient.</p>
  
  <p>The first one is when the value is 100. The progress bar is full and it show the whole gradient.</p>
  
  <p>But when the progressbar's value is 50, I get the second result. a 50% filled bar with the whole gradient.</p>
  
  <p>What I want to archieve is the third one, when the bar's value is 50, the gradient has to be 50% also.</p>
  
  <p>How can I archieve that? Opacity mask? (First guess but maybe I'm wrong).</p>
  
  <p>Well, I appreciate some help. Thanks!</p>