Событие при изменении количества товара в заказе из административной части

AddEventHandler( 'sale', 'OnBeforeOrderUpdate', 'OnBeforeOrderUpdateHandler' );

function OnBeforeOrderUpdateHandler($ID, $arFields) {

$dbBasketItems = CSaleBasket::GetList(

                             array( "NAME" => "ASC", "ID" => "ASC" ),

                             array( 

                                    "ORDER_ID" => $ID ),

                             false,

                             false,

                             array("ID", "CALLBACK_FUNC", "MODULE", "PRODUCT_ID", "QUANTITY", "PRODUCT_PROVIDER_CLASS"));   
 
        while ($arItems = $dbBasketItems->Fetch())

        {

           ...

        }


}