Avoid multiple instances of a program -> INCL. PARAMETER PASSING to already running instance

Question

Hey Guys,

I am programming a timer thats shuts down Windows automatically after a certain time. When I start the program, it adds 30 mins to a counter and counts them down. Because it doesn't make sense to have multiple timers at once, I wanted my program to run in only ONE instance - this works fine like this.

    static class Program
    {
        /// <summary>
        /// Der Haupteinstiegspunkt für die Anwendung.
        /// </summary>
        [STAThread]
        static void Main(string[] args)
        {
            Mutex Mu = new Mutex(false, "{XEQRT97T57B1PNGJ1LRG83JEKGLUWX10}");
            if (Mu.WaitOne(0, false))
            {
                Application.EnableVisualStyles();
                Application.SetCompatibleTextRenderingDefault(false);
                Application.Run(new Form1(true));
            }
            else
            {
                // ADD MORE TIME TO THE ALREADY RUNNING TIMER
            }
        }
    }

I placed the actualy timer in a Form class, so I can put it nicely into the system tray.. The thing I want to do is the following.
When I first start the program, it adds 30 minutes to the timer and it starts to count down, if I start the program the second time, I don't want it to create a second instance. Instead I want to give my already running instance a sign to add another 30 minutes on the already counting timer. It is supposed to simulate the Sleep function of a normal hifi system. Is there any possibilty to do that?!

Here is my Form1 class for completion.

    public partial class Form1 : Form
    {
        public Int32 timeToShutdown = 0;
        public Int16 standardIntervalStep = 30; // in Minuten

        public Form1(Boolean addMoreMinutes)
        {
            if (addMoreMinutes == true)
            {
                InitializeComponent();
                this.startMinimized();
            }

            this.timeToShutdown = this.getTimeFromCommandLine();
            this.setTimer(this.timeToShutdown);
        }

        public void startMinimized()
        {
            this.WindowState = FormWindowState.Minimized;
            this.ShowInTaskbar = false;
        }

        public Int32 getTimeFromCommandLine()
        {
            string[] args = Environment.GetCommandLineArgs();
            foreach (String arg in args)
            {
                try
                {
                    this.timeToShutdown += Convert.ToInt32(arg);
                }
                catch (Exception)
                {
                    this.timeToShutdown += this.standardIntervalStep;
                }

            }

            // Es werden Minuten eingegeben, jetzt muss das in Millisekunden umgerechnet werden
            Int16 minutesToShutdown = Convert.ToInt16(timeToShutdown);
            timeToShutdown = timeToShutdown * 60 * 1000;

            DateTime shutdownTime = DateTime.Now.AddMilliseconds(timeToShutdown);
            this.systemTrayIcon.ShowBalloonTip(500, "Shutdown", "Windows wird in " + minutesToShutdown + " Minuten heruntergefahren. (" + shutdownTime + ")", ToolTipIcon.Info);

            return this.timeToShutdown;
        }

        public void setTimer(Int32 milliSeconds)
        {
            Timer shutdownTimer = new Timer();
            shutdownTimer.Interval = milliSeconds;
            shutdownTimer.Tick += new EventHandler(exitWindows);
            shutdownTimer.Start();
        }

        public void exitWindows(object sender, EventArgs e)
        {
            this.systemTrayIcon.ShowBalloonTip(500, "Shutdown", "Windows wird heruntergefahren.", ToolTipIcon.Info);
            StartShutDown("-f -s -t 5");
        }

        private static void StartShutDown(string param)
        {
            ProcessStartInfo proc = new ProcessStartInfo();
            proc.FileName = "cmd";
            proc.WindowStyle = ProcessWindowStyle.Hidden;
            proc.Arguments = "/C shutdown " + param;
            Process.Start(proc);
        }


        private void closeShutdown_Click(object sender, EventArgs e)
        {
            Application.Exit();
        }

Maybe somebody can help me out with this, I would really appreciate that..
greets pat