Select e.DataCol.Name

    Case "销售日期","代码"

        If e.DataRow.IsNull("销售日期") OrElse e.DataRow.IsNull("代码") Then

            e.DataRow("销售单编号") = Nothing

        Else

            Dim dg As Date = e.DataRow("销售日期")

            Dim yg As Integer = dg.Year

            Dim mg As Integer = dg.Month

            Dim Days As Integer = Date.DaysInMonth(yg,mg)

            Dim fdg As Date = New Date(yg,mg,1) \'获得该月的第一天

            Dim ldg As Date = New Date(yg,mg,Days) \'获得该月的最后一天

            Dim bhg As String = e.DataRow("代码") & "-" & Format(dg,"yyyyMM") & "-"  

            If e.DataRow("销售单编号").StartsWith(bhg) = False \'如果单据编号前缀不符

                Dim maxg As String

                Dim idxg As Integer

                Dim fltg As String

                fltg = "代码 = \'"& e.DataRow("代码") & "\' And 销售日期 >= #" & fdg & "# And 销售日期 <= #" & ldg & "# And [_Identify] <> " & e.DataRow("_Identify")

                maxg = e.DataTable.Compute("Max(销售单编号)",fltg)  

                If maxg > "" Then \'如果存在最大单据编号

                    idxg = CInt(maxg.Substring(12,3)) + 1 

                Else

                    idxg = 1 \'否则顺序号等于1

                End If

                e.DataRow("销售单编号") = bhg & Format(idxg,"000")

            End If

        End If

End Select