title: RoutedCommands that use tunneling instead of bubbling
body: <p>I have a custom control (<code>MyControl</code>) that exposes a custom command. I want the parent <code>Window</code> to be able to invoke this command, and all <code>MyControls</code> should react to it.</p>
  
  <p>I have added the command to <code>MyControl</code>'s <code>CommandBindings</code> collection, which also provides a <code>CanExecute</code> callback that always returns true.</p>
  
  <p>My problem is that a menu item that invokes this command never gets enabled. I'm presuming this is because the menu is above the <code>MyControls</code> in the visual tree, but to be honest I'm a little fuzzy on how <code>RoutedUICommand</code>'s scope works exactly.</p>
  
  <p>Can someone clarify what I'm doing wrong, or if this is even possible?</p>