function showShippingAddress(show_b) {
  if (show_b) {
    $('shipping_address').show();
    $('same_shipping_note').hide();
  } else {
    $('shipping_address').hide();
    $('same_shipping_note').show();
  }
}

var address_behaviour_rules = {
  '#use_diff_shipping' : function(el) {
    el.onclick = function() {
      showShippingAddress(el.checked);
    }
  }
}

Behaviour.register(address_behaviour_rules);