Private Sub MausKreisen()
    Dim Center As Point = New Point(150, 150)
    Dim Radius As Double = Center.Y / 2

    Dim X As Double
    Dim Y As Double
    Dim Grad As Double

    Do
      Grad += 1
      X = Center.X + Math.Cos((Grad / 360) * 2 * Math.PI) * Radius
      Y = Center.Y + Math.Sin((Grad / 360) * 2 * Math.PI) * Radius

      Dim pt As New Point(CInt(X), CInt(Y))
      Windows.Forms.Cursor.Position = Me.PointToScreen(pt)
      System.Threading.Thread.Sleep(5)
      Application.DoEvents()
    Loop Until Grad > 360
  End Sub

  Private Sub CheckBox1_CheckedChanged(ByVal sender As _
        System.Object, ByVal e As System.EventArgs) Handles _
        CheckBox1.CheckedChanged
    If CheckBox1.Checked Then
      KreisZeichnen()
    Else
      Me.Refresh()
    End If
  End Sub

  Private Sub KreisZeichnen()
    Dim Center As Point = New Point(150, 150)
    Dim Radius As Double = Center.Y / 2

    Dim g As Graphics = Me.CreateGraphics
    g.TranslateTransform(Center.X, Center.Y)
    Dim rect As New Rectangle(CInt(-Radius), CInt(-Radius), _
          CInt(Radius * 2), CInt(Radius * 2))

    Static red As Boolean
    red = Not red
    If red Then
      g.DrawEllipse(Pens.Red, rect)
    Else
      g.DrawEllipse(Pens.BlueViolet, rect)
    End If
    g.DrawEllipse(Pens.Red, 0, 0, 1, 1)
  End Sub