title: extjs4 : chained combo
body: <p>I'm trying to add some dynamic data into a "livesearch" combo box.</p>
  
  <p>I've a set of 2 combos.</p>
  
  <p>The first one allow you to select some data.
  The second combo is a "livesearch" combo that should have a dynamic parameter from the first combo.
  So the 2nd combo is linked to a model, which is linked to a datastore that queries the server and outputs the data. But that data has to be filtered according to the first combo parameter...</p>
  
  <p>Anyone knows how to do that ?</p>