回答編集履歴

  function fnSetClassCategories(form, classcat_id2_selected) {

  var $form = $(form);

  var product_id = $form.find('input[name=product_id]').val();

  var elem = document.getElementById("select2");

  if ($form.find('select[name=classcategory_id1]').val() == "__unselected") {

  elem.innerHTML = "<select disabled name='classcategory_id2' style='<!--{$arrErr.classcategory_id1|sfGetErrorColor}-->'>";

  } else {

  elem.innerHTML = "<select name='classcategory_id2'style='<!--{$arrErr.classcategory_id1|sfGetErrorColor}-->'>";

  }

  var $sele1 = $form.find('select[name=classcategory_id1]');

  var $sele2 = $form.find('select[name=classcategory_id2]');

  setClassCategories($form, product_id, $sele1, $sele2, classcat_id2_selected);