title: Replace a UIViewController in the UINavigationController hierarchy
body: <p>I have an iPhone app which uses a standard implementation of <code>UINavigationController</code> for the app navigation.</p>
  
  <p>I am trying to figure out a way to replace a view controller in the hierarchy.
  In other words, my app loads into a <code>rootViewController</code> and when the user presses a button, the app pushes to <code>firstViewController</code>. Then the user pushes another button to navigate the app to <code>secondViewController</code>. Again the use navigates down to another view controller, thirdViewController. However, I want the BackButton of the <code>thirdViewController</code> to pop back to firstViewController. </p>
  
  <p><strong>Essentially, when the user pushes to <code>thirdViewController</code>, I would like it to replace <code>secondViewController</code> in the navigation hierarchy.</strong></p>
  
  <p><strong>Is this possible?</strong> I know it is using Three20, but I'm not in this case. Nevertheless, if it's possible in Three20, then it certainly should be using straight SDK calls. Does anyone have any thoughts?</p>
  
  <p>Cheers,
  Brett</p>