function dynamicSelect(id1, id2) {
 var agt = navigator.userAgent.toLowerCase();
 var is_ie = ((agt.indexOf("msie") != -1) && (agt.indexOf("opera") == -1));
 var is_mac = (agt.indexOf("mac") != -1);
 if (!(is_ie && is_mac) && document.getElementById && document.getElementsByTagName) {
  var sel1 = document.getElementById(id1);
  var sel2 = document.getElementById(id2);
  var clone = sel2.cloneNode(true);
  var clonedOptions = clone.getElementsByTagName("option");
  refreshDynamicSelectOptions(sel1, sel2, clonedOptions);
  sel1.onchange = function() {
   refreshDynamicSelectOptions(sel1, sel2, clonedOptions); };
 }
}

function refreshDynamicSelectOptions(sel1, sel2, clonedOptions) {
 while (sel2.options.length) {
  sel2.remove(0); }
 var pattern1 = /( |^)(select)( |$)/;
 var pattern2 = new RegExp("( |^)(" + sel1.options[sel1.selectedIndex].value + ")( |$)");
 for (var i = 0; i < clonedOptions.length; i++) {
  if (clonedOptions[i].className.match(pattern1) || clonedOptions[i].className.match(pattern2)) {
   sel2.appendChild(clonedOptions[i].cloneNode(true)); }
 }
 var selected_model = document.getElementById("selected_model");
 if (selected_model) {
  setTimeout('selected_model.selected = true', 0); }
}