function cascadingDropDownList(parent, child, isSubselectOptional, childVal, defaultVal) {

	if (typeof defaultVal == "undefined"){
		defaultVal = "エリアを選択して下さい";
	}
	jQuery("body").append("<select style='display:none' id='" + parent + child + "'></select>");
	jQuery("#" + parent + child).html(jQuery("#" + child + " option"));

	var parentValue = jQuery("#" + parent).attr("value");
	jQuery("#" + child).html(jQuery("#" + parent + child + " .sub_" + parentValue).clone());

	if (isSubselectOptional){
		jQuery("#" + child).prepend("<option value='0'> "+defaultVal+" </option>");
	}
	childVal = (typeof childVal == "undefined") ? "" : childVal;
	jQuery("#" + child + ' option[@value="' + childVal + '"]').attr("selected", "selected");



	jQuery("#" + parent).change(function() {
		var parentValue = jQuery("#" + parent).attr("value");
	    jQuery("#" + child).html(jQuery("#" + parent + child + " .sub_" + parentValue).clone());
		if (isSubselectOptional){
			jQuery("#" + child).prepend("<option value='0'> "+defaultVal+" </option>");
		}
		jQuery("#" + child).trigger("change");
		jQuery("#" + child + ' option[@value="0"]').attr("selected", "selected");
		jQuery("#" + child).focus();
  });
}