Help with Timer and BackgroundWorker

[kokon]

Hi, After starting below code, the output I got is:
-------------
day
minute
day
minute,minute
day
minute,minute,minute
--------------
It should be:
--------------
day
minute,
day
minute
day
minute
--------------
I don`t knowo why the backgroud worker starts more then 1 time on each steps, is Background worker cancelletion working right?
Please help.

        private void Form1_Load(object sender, EventArgs e)
        {
          

            timer1.Interval = 3000;
            timer1.Tick += new EventHandler(DayTicker);
            timer1.Start();
        }
        
        public void DayTicker(object sender, EventArgs e)
        {
            timer1.Stop();
            if (backgroundWorker1.IsBusy) backgroundWorker1.CancelAsync();
            if (backgroundWorker1.CancellationPending) return;
           
            richTextBox1.Text += "\n day   \n";

            backgroundWorker1.WorkerReportsProgress = true;
            backgroundWorker1.WorkerSupportsCancellation = true;
            backgroundWorker1.DoWork += new DoWorkEventHandler(bw_DoWork_day);
            backgroundWorker1.RunWorkerAsync("test");
            backgroundWorker1.RunWorkerCompleted += bw_workerday_coplete;
            
        }

        public void bw_DoWork_day(object sender, DoWorkEventArgs e)
        {
            string w = "minute";
            e.Result = 1;

            e.Cancel = true;

            if (InvokeRequired)
                Invoke(new Change(OnChange), w);
        }

        public void bw_workerday_coplete(object sender, RunWorkerCompletedEventArgs e)
        {
           if (e.Error != null)
                MessageBox.Show("Worker exception: " + e.Error.ToString());
            else if (e.Cancelled)
            {
                timer1.Tick += new EventHandler(DayTicker);
                timer1.Start();
            }
         }

        private void OnChange(string w)
        {
            richTextBox1.Text += w + ",";
            Application.DoEvents();
        }

        private delegate void Change(string w);
    }
}