Kako proslijediti SHIFT + taster koristeci PostMessage() ?

Dakle kako poslati SHIFT, CTRL ili ALT aplikaciji koja radi u pozadini koristreci PostMessage() funkciju.

Poslije obimnijegog guglanja nasao sam da bi ovo trebalo da radi:

public partial class Form1 : Form
    {


        [DllImport("user32.dll", SetLastError = true)]
        static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

        [DllImport("user32.dll", EntryPoint="PostMessage", CallingConvention=CallingConvention.Winapi)]
        public static extern bool PostMessage(IntPtr hWnd, uint msg, uint wParam, uint lParam);

        [DllImport("user32.dll")]
        static extern byte VkKeyScan(char ch);

        const uint WM_KEYDOWN = 0x100;
        const uint WM_KEYUP = 0x101;

        const uint VK_CONTROL = 0x11; //virtual key code za Ctrl

        //provjerava da li je proces startovan
        private bool IsProcessStarted(string processName)
        {

            foreach (Process clsProcess in Process.GetProcesses())
            {
                if (clsProcess.ProcessName.Contains(processName))
                {
                    return true;
                }

            }

            return false;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (IsProcessStarted("notepad") == true)
            {
                try
                {
                    Process[] procs = Process.GetProcessesByName("notepad");

                    foreach (Process proc in procs)
                    {
                        if (proc.MainWindowTitle == "Untitled - Notepad")
                        {
                            IntPtr hWnd = FindWindowEx(proc.MainWindowHandle, IntPtr.Zero, "edit", null);
                          
                
                            PostMessage(hWnd, WM_KEYDOWN, VK_CONTROL, 0);   //pritiska Ctrl
                            PostMessage(hWnd, WM_KEYDOWN, VkKeyScan('S'), 0);  //pritiska 'S'

                            PostMessage(hWnd, WM_KEYUP, VkKeyScan('S'), 0);        //otpusta Ctrl
                            PostMessage(hWnd, WM_KEYUP, VK_CONTROL, 0);        //otpusta 'S'
                       

                          
                        }
                    }
                }
                catch
                {
                    MessageBox.Show("Greska!", "Upozorenje!", MessageBoxButtons.OK, MessageBoxIcon.Information);
                }
            }

            else
            {
                MessageBox.Show("Notepad nije starovan", "Upozorenje!", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
            }


        }

   }

međutim ni ovo ne radi, a vidio sam da nisam jedini kome ovo ne radi. Doduše, svakim klikom dvaput upisuje 's'. Jel ima neko ideju kako da ovo proradi? :) Samo da napomenem, potrebno mi je da ovo radi sa PostMessage jer na taj nacin mogu poslati sekvencu tastera i procesu u pozadini.

Neko? :)