05.08.2014 AddEventHandler("main", "OnAdminTabControlBegin", "orderCanselReason");
function orderCanselReason(&$form)
{
  if ($GLOBALS["APPLICATION"]->GetCurPage() == "/bitrix/admin/sale_order_detail.php")
  {
   CJSCore::Init('jquery');
   //echo "<pre>"; print_r($form); echo "</pre>";
   $form->arFields['ORDER_CANCELED']['custom_html'] .= '<script>
    function reasoncheck(e)
    {
     if ($("#FORM_REASON_CANCELED").val() == "")
     {
      e.preventDefault();
      if (e.stopPropagation)
      {
       e.stopPropagation();
      }
      else
      {
       window.event.cancelBubble = true;
      }
      alert("Пожалуйста, введите причину отмены!");
     }
    }
    $(document).ready(function() {
     $(".adm-detail-content-cell-r").delegate(".adm-btn-wrap", "click", function() {
      $(".popup-window-button-text").each(function() {
       if ($(this).html() == "Сохранить") $(this).attr("onclick", "reasoncheck(event);");
      });
     });
    });
   </script>';
  }
}