"[productname]='" & Me![ProductName] & "'")
PName = Forms!salesinvoices!SalesDetails!ProductName
PCode = Forms!salesinvoices!SalesDetails!ProductCode
PKind = Forms!salesinvoices!SalesDetails!Kind
CostPrice = DLookup("[price]", "products", "[productname]='" & [PName] & "'and [productcode]='" & [PCode] & "'and [kind]='" & [PKind] & "'")