C#

private void button2_Click(object sender, EventArgs e)
{
   // Create ttimer
    System.Timers.Timer Timer;
    Timer = new System.Timers.Timer();
    Timer.Interval = 20; // Timer Intervall = 20 ms
    Timer.Enabled = true;

    Timer.Elapsed += new ElapsedEventHandler(OnTimedEvent);
}

private void OnTimedEvent(object source, ElapsedEventArgs e)
{
    // Invoke, since it`s anoter thread (?)
    Invoke(new MethodInvoker(delegate
    {
        // add 20 to the value in the textbox
        label1.Text = (Convert.ToInt32(label3.Text) + 20).ToString();
    }));
}