SELECT Bills.Bill_ID, Sales.Sales_Item, Sales.Sales_Item_Unit, Last(Sales.Sales_Price) AS LastOfSales_Price
FROM Bills INNER JOIN Sales ON Bills.Bill_ID = Sales.Bill
GROUP BY Bills.Bill_ID, Sales.Sales_Item, Sales.Sales_Item_Unit
HAVING (((Bills.Bill_ID)=[Forms]![Bills]![SalesONBills].[Form]![Bill]) AND ((Sales.Sales_Item)=[Forms]![Bills]![SalesONBills].[Form]![Sales_Item]) AND ((Sales.Sales_Item_Unit)=[Forms]![Bills]![SalesONBills].[Form]![Sales_Item_Unit]));