function setElementClassById(elem,value) {
   if(document.getElementById) {
         var obj = document.getElementById(elem);
         if(obj) {
            obj.className = value;
         }
   }
}
function switchRequiredItem(id,flg){
  tmp_array = new Array(3);
  for(var i=1;i<tmp_array.length;i++){
    tmp_array[i] = new Array(1);
    //tmp_array[i]["class"] = "";
    tmp_array[i]["element"] = "";
  }
  tmp_array[1]["element"] = "tel";
  tmp_array[2]["element"] = "fax";
  //tmp_array[id]["class"] = "must";
  if(flg){
    var tmp_class = "must";
  }else{
    var tmp_class = "";
  }
  setElementClassById(tmp_array[id]["element"], tmp_class);
}