Select Case e.DataCol.Name

    Case "年","月","店名","对账品名"

        Dim dr As DataRow = e.DataRow

        Dim pr As DataRow

        If dr.IsNull("年") OrElse dr.IsNull("月") OrElse dr.IsNull("店名") OrElse dr.IsNull("对账品名") Then

            dr("月初柜台余货_数量") = Nothing

        Else

            Dim filter As String

            filter = "店名 = \'" & dr("店名") & "\' And 对账品名 = \'" & dr("对账品名") & "\'"

            Dim d As Date = cdate(dr("年"),dr("月"),1)

            d = d.AddMonths(-1)

            filter = filter & " and 年=" & d.Year & " And 月=" & d.Month

            pr = DataTables("产品").Find(filter)

            If pr IsNot Nothing Then

                dr("月初柜台余货_数量") = pr("月末柜台余货_数量")

            End If

        End If

End Select