$(document).ready(function() {
   
   // register the region select box ajax
   $('select#id_region').change(function() {
      var val = $(this).val();
      var url = 'ajax-states-by-region/';
      if (val != '')
         url += val + '/';
      // replace the multiple states multiple select
      $('#states_select').load(url);
   });
});