function dyn_select() {
  ex_type = "dyn_select";
  myUrl = "dyn_select.php";

  var param = document.getElementById("RegionID").value;
  myUrl += "?param="+param;

  var myOriginal = document.getElementById("city_select_original");
  var myNew = document.getElementById("city_select_new");

  if (param == 0) {
    myOriginal.style["display"] = 'inline';
    myNew.style["display"] = 'none';
  } else {
    myOriginal.style["display"] = 'none';
    loadData(myUrl);
  }
}