主题：请求修改代码

Select e.DataCol.Name
    Case "班级编号","类别"
        If e.DataRow.IsNull("班级编号") OrElse e.DataRow.IsNull("类别") Then
            e.DataRow("教材编号") = Nothing
        Else
            Dim bh As String  = e.DataRow("班级编号") & e.DataRow("类别")
            If e.DataRow("教材编号").StartsWith(bh) = False '如果教材编号前缀不符
                Dim max As String
                Dim idx As Integer
                Dim flt As String
                flt = "类别 = '"& e.DataRow("类别") & "' And 班级编号 = '" & e.datarow("班级编号") & "' And [_Identify] <> " & e.DataRow("_Identify")
                max = e.DataTable.Compute("Max(教材编号)",flt) '取得该月的相同类的最大教材编号
                If max > "" Then '如果存在最大教材编号
                    idx = CInt(max.Substring(bh.length)) + 1 '获得最大教材编号的后四位顺序号,并加1
                Else
                    idx = 1 '否则顺序号等于1
                End If
                e.DataRow("教材编号") = bh & Format(idx,"00")
            End If
        End If
End Select