how to use System.Timers.Timer to control a progress in winform

public partial class Form1 : Form
    {
        System.Timers.Timer aTimer;
        public Form1()
        {
            InitializeComponent();
            aTimer = new System.Timers.Timer();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            aTimer = new System.Timers.Timer(2000);
            aTimer.Elapsed += new System.Timers.ElapsedEventHandler(aTimer_Elapsed);
            aTimer.Enabled = true;
            int n = Convert.ToInt32(textBox1.Text);
            long m = ComputeFibonacci(n);
            Console.WriteLine("Fibonacci：" + m);
            aTimer.Enabled = false;
        }
         void aTimer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
        {
            Console.WriteLine("The Elapsed event was raised at {0}", e.SignalTime);
            if (InvokeRequired)
            {
                this.Invoke(new Action(progressBar1.PerformStep));
                Application.DoEvents();
            }
            else
            {
                progressBar1.PerformStep();
                Application.DoEvents();
            }
            Console.WriteLine(progressBar1.Value);
        }
        /// <summary>
         /// Compute  Fibonacci
        /// </summary>
        /// <param name="n"></param>
        /// <returns></returns>
        long ComputeFibonacci(int n)
        {
            // The parameter n must be >= 0 and <= 91.
            // Fib(n), with n > 91, overflows a long.
            if ((n < 0) || (n > 91))
            {
                throw new ArgumentException(
                    "value must be >= 0 and <= 91", "n");
            }
            long result = 0;
            // Abort the operation if the user has canceled.
            // Note that a call to CancelAsync may have set 
            // CancellationPending to true just after the
            // last invocation of this method exits, so this 
            // code will not have the opportunity to set the 
            // DoWorkEventArgs.Cancel flag to true. This means
            // that RunWorkerCompletedEventArgs.Cancelled will
            // not be set to true in your RunWorkerCompleted
            // event handler. This is a race condition.
            if (n < 2)
            {
                result = 1;
            }
            else
            {
                result = ComputeFibonacci(n - 1) +
                         ComputeFibonacci(n - 2);
            }

            return result;
        }