title: Check boxes just on tree leaf nodes in Flex
body: <p>I'm having difficulty getting checkboxes on <strong>only</strong> the leaf nodes of a tree.</p>
  
  <p>Before anyone links it, I've seen <a href="http://www.sephiroth.it/file_detail.php?id=151#" rel="nofollow noreferrer">http://www.sephiroth.it/file_detail.php?id=151#</a> and this isn't exactly what I need. I don't want a 3-state checkbox system including both branch and leaf.</p>
  
  <p>I understand applying the checkbox item renderer to a data grid but not on a tree.</p>
  
  <p>I'm using Flex Builder 3</p>