Return to default value

Return to default value

Hi:
I have this simple code for change combos based on selection.
  1. $("#manufacturer_id").change(function(){
  2.       $.ajax({
  3.          url: 'index.php?route=catalog/product/getConsignaManufacturer&token=<?php echo $token; ?>&manufacturer_id=' + $('#manufacturer_id').val(),
  4.          type: 'GET',
  5.          dataType: 'json',
  6.          success: function(data) {
  7.             $.each(data, function(){
  8.                $("#consigna_id").empty().removeAttr("disabled").append('<option value="'+this.consigna_id+'">' + this.consigna_code + '</option>');
  9.             });
  10.          }
  11.       });
  12.    });
This works perfectly. Now the mail combo have a option value="0" with title "Please select one" so if not change happen then the second combo never is activated. How when the user select the first option "Please select one" in the main combo (#manufacturer_id) I can disable the second combo?
Cheers and thanks in advance