for example 	

function getFlyX_partOne($aFormValues){
  $objResponse = new xajaxResponse();
  
  $objResponse->call("y");
  $objResponse->call("xajax_getFlyX_partTwo", $aFormValues);

  return $objResponse;
}

function getFlyX_partTwo($aFormValues){
  $objResponse->assign("btnSubmit","value","xxx");
  $objResponse->assign("btnSubmit","disabled","");

  ... do something else useful here ...
  
  return $objResponse;
}