title: Combobox contents based on another combobox value
body: <p>I have two comboboxes where the first one has categories (and I can fill that easily from the source file).  The trick is having the second combobox show only the items that are associated with the chosen category from the first combobox.  For example:</p>
  
  <p>cb1 is populated from a sourcefile with the category values 1, 2, 3 &amp; 4 and cb2 is populated with values A,B,C,D,E,F,G,H</p>
  
  <p>What I am failing at doing is limiting what is seen in cb2.  So when cb1's value is "1", I only want "A" and "B" to be visible in cb2, and if cb1 changes to "2" I only want "C" and "D" to be visible.  </p>