Question : better way to retreive a value for the last entry in a table

I have tables related to purchases that hold products and qty ordered values for each customer order.
Im trying to return a value for qty the last time an order was placed for a particular product.
The follow code works but I'd like to know a better way to do it please?
-- find the last purchase for a product for each customer that placed an order within a specific time frame
SELECT     MAX(dbo.tbPurchaseItem.iPurchaseId) AS LastPurchase, dbo.tbPurchase.iCustomerId
into #tmp
FROM         dbo.tbProduct x INNER JOIN
                      dbo.tbPurchaseItem ON x.iProductId = dbo.tbPurchaseItem.iProductId INNER JOIN
                      dbo.tbPurchase ON dbo.tbPurchaseItem.iPurchaseId = dbo.tbPurchase.iPurchaseId
WHERE     (x.iProductId = 11 OR
                      x.iProductId = 22) AND (dbo.tbPurchase.dtPurchase > '01 mar 2010')
GROUP BY dbo.tbPurchase.iCustomerId
 -- find the qty ordered for the products in the last order
SELECT    dbo.tbPurchaseItem.iQty as TotalQty,  dbo.tbPurchase.iCustomerId
FROM         dbo.tbProduct x INNER JOIN
                      dbo.tbPurchaseItem ON x.iProductId = dbo.tbPurchaseItem.iProductId INNER JOIN
                      dbo.tbPurchase ON dbo.tbPurchaseItem.iPurchaseId = dbo.tbPurchase.iPurchaseId
WHERE     (x.iProductId = 11 OR
                      x.iProductId = 22) and dbo.tbPurchaseItem.iPurchaseId in
(select LastPurchase
from #tmp)

Thanks!

Answer : better way to retreive a value for the last entry in a table

In SAP, there is no total summed amount for Purchase Requisition...