我的问题是怎样实现PrintDocument的分页打印？

以下一部分代码：（PrintDocument挂钩的事件是A4纸的20张长度，可以打印，但不能指定从M页到N页打印，化了好几天了都没有搞定，请教各位了。



  Private PrintDataGrid As PrintDocument

  Private PrintPriview As PrintPreviewDialog

  Private PageSetup As PageSetupDialog



 Public Sub Print()
        Try

            PrintDataGrid = New System.Drawing.Printing.PrintDocument

            AddHandler PrintDataGrid.PrintPage, AddressOf Me.PrintDataGrid_PrintPage

            PageSetup = New PageSetupDialog

            PageSetup.PageSettings = PrintDataGrid.DefaultPageSettings


            If PageSetup.ShowDialog() = DialogResult.Cancel Then
                Exit Sub
            End If


            If PrintDataGrid.DefaultPageSettings.PaperSize.PaperName.ToString = "custom" Then
                ' PrintDataGrid.DefaultPageSettings.PaperSize.Kind = System.Drawing.Printing.PaperKind.A4
            End If

            allpages = 1

            PageNumber = 1

            index_Rows = 0


            PrintDataGrid.DefaultPageSettings.PrinterSettings.FromPage = frompage//全局变量

            PrintDataGrid.DefaultPageSettings.PrinterSettings.ToPage = topage//全局变量



            Dim printerset As PrintDialog = New PrintDialog

            printerset.Document = PrintDataGrid

            printerset.ShowNetwork = True

            printerset.AllowSelection = True

            printerset.AllowSomePages = True

            printerset.ShowDialog()


            PrintPriview = New PrintPreviewDialog

            PrintPriview.AutoScroll = True

            PrintPriview.ControlBox = True

            PrintPriview.AllowDrop = True

            PrintPriview.FormBorderStyle = FormBorderStyle.SizableToolWindow

            PrintPriview.Document = PrintDataGrid

            PrintPriview.Size = New Size(600, 600)

            PrintPriview.StartPosition = FormStartPosition.CenterScreen

            PrintPriview.SetAutoScrollMargin(5, 5)

            PrintPriview.ShowDialog()


        Catch ex As Exception
            MessageBox.Show("error:" & ex.ToString)
        Finally

        End Try
    End Sub


Private Sub PrintDataGrid_PrintPage(ByVal sender As Object, ByVal ev_p As System.Drawing.Printing.PrintPageEventArgs)
        On Error Resume Next

        Dim DrawBrush As New SolidBrush(正文颜色)

        Dim row_count As Integer '当前要打印的行

        Dim myrow As DataRow

        Dim 列宽(DataGridTable.Columns.Count - 1) As Single

        Dim 列高(DataGridTable.Columns.Count - 1) As Single

        ev = ev_p.Graphics

        Dim x_unit_all As Single

        Dim 最多行数 As Single

        Dim mypoint As PointF

        Dim 数据行数 As Integer = 0

.....................
end sub