C#

int i=0;
Timer tmrTest = new Timer();

public void OnTimerEvent_test(object source, EventArgs e)
{
   i++;
   txtCounter.Text = i.ToString();
}

private void btnStartTimer_Click(object sender, EventArgs e)
{
   tmrTest.Enabled = true;
   tmrTest.Interval = 500;
   tmrTest.Tick += new System.EventHandler(OnTimerEvent_test);
}

private void btnStopTimer_Click(object sender, EventArgs e)
{
   tmrTest.Enabled = false;
}