UPDATE dbo.Items
>>			SET Items.iqtyonhand = Items.iqtyonhand + Deleted.trn_qty - Inserted.trn_qty
>>		FROM dbo.Items
>>			INNER JOIN Inserted ON Items.iItemid = Inserted.trn_itmfk
>>			INNER JOIN Deleted ON Items.iItemID = Deleted.trn_itmfk
>>		WHERE iItemTypId = '43'

>;with cteChanges AS (SELECT D.trn_itmfk AS ItemID, SUM(COALESCE(D.trn_qty,0) - COALESCE(I.trn_qty,0)) as ChangedQty
>FROM Deleted D INNER JOIN Inserted I on D.trn_itmFk = I.trn_itmFK
>GROUP BY D.trn_itmfk)
>
>MERGE dbo.Items as Trg
>USING cteChanges as Src ON Trg.ItemId = Src.ItemID
>WHEN MATCHED and Trg.iItemTypeId = '43' 
>THEN UPDATE SET iQtyOnHand = COALESCE(Trg.iQtyOnHand) + ChangedQty;