$(document).ready(function() {
      
   // load job types via ajax
   $('#id_job_area').change(function() {
      
      // keep track of the old type
      var old_type = $('#id_job_type').val()
      
      // load the new list of types
      $('#id_job_type').load(
         window.location + 'ajax-types/', 
         { area: $(this).val() },
         function(responseText, textStatus, XMLHttpRequest) {            
            if (textStatus == 'success')
               $(this).val(old_type);
         }
      )
   });
});