How To open a popup editor window  from the Tree Widget

How To open a popup editor window  from the Tree Widget

  
Hi all,
I have the tree widget implemented in my application and I need to open a popup editor when a node or leaf in the tree is clicked.

I assigned the name of one of my applications webpages  to the URL field of the tree widget record ( "/eSpaceName/webscreenName.aspx")
Since the source web block type of this page is: "common\Layout_Popup"  i was hoping the page would open as a popueditor, like it does when I call it from a link within another webpage.
The page still opens but as standard webpage.
How can make this page open as a popup editor?
Any help is appreciated very much.
Thanks
Joerg