function copy_listbox(tgt,src) {
   var lb=document.getElementById(tgt);
   // clear the input listbox
  for (var i=lb.options.length-1; i>=0; i--){
     lb.options[i] = null;
   }
   lb.selectedIndex = -1;
   // restore it

   var bk=document.getElementById(src);
   for (var i=bk.options.length-1; i>=0; i--){
     oOption = document.createElement("OPTION");
     // Append to end of list
    oOption.text = bk.options[i].text;
     oOption.value = bk.options[i].value;
     oOption.selected = false;
     lb.options[lb.options.length] = oOption;
   }
 }