title: How to detect when a pressed mouse enters a widget in a different Frame
body: <p>I have a ttk Treeview (in a Frame in a Tk)) and a tk Listbox (in a Toplevel). My intention is to do the following:</p>
  
  <ol>
  <li>press mouse button 1 in the Treeview</li>
  <li>move (the pressed) mouse over to the Listbox</li>
  <li>set the focus to the Toplevel containing the Listbox when the mouse enters</li>
  </ol>
  
  <p>Right now I can set the focus of the Toplevel when an unpressed mouse enters. I used <code>.bind("&lt;Enter&gt;")</code>.</p>
  
  <p>When I use <code>.bind("&lt;B1-Motion&gt;")</code> I can detect movement of a pressed mouse. But only if I pressed the mouse within the list.</p>
  
  <p>When I use<code>.bind("&lt;B1-Enter&gt;")</code>I don't get any events.</p>
  
  <p>How can I detect if a somewhere else pressed mouse enters my Listbox?</p>