Dim flag As Boolean = True
    Dim myBitmap As Bitmap
    Private Sub Panel2_Paint(ByVal sender As System.Object, ByVal e As _
      System.Windows.Forms.PaintEventArgs) Handles Panel2.Paint
        Dim gr As Graphics = e.Graphics
        If flag = True Then
            Dim myPen As Pen = New Pen(Color.Black)
            Dim i As Int32
            For i = 0 To Panel2.Width Step 10
                gr.DrawLine(myPen, i, 0, i, Panel2.Height)
            Next
        End If
        Try
            gr = Graphics.FromImage(myBitmap)
        Catch
        End Try
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        myBitmap = New Bitmap(Panel2.Width, Panel2.Height)
        Panel2.BackgroundImage = New Bitmap(myBitmap)
        flag = False
    End Sub