// Create an instance of HookProc.
StartHookProcedure = new CallBack(StartHookProc);
IntPtr desktop = FindWindowEx(
  IntPtr.Zero, IntPtr.Zero, "Progman", null);
uint procId = 0;
uint threadId = GetWindowThreadProcessId(desktop, out procId);
Process process = Process.GetCurrentProcess();
ProcessModule module = process.MainModule;

IntPtr hModule = GetModuleHandle(null); // get my module handle...
//IntPtr start = FindWindowEx(desktop, IntPtr.Zero, "Button", null);

hHook = SetWindowsHookEx(WH_GETMESSAGE,
  StartHookProcedure, hModule, (int)threadId);
//If the SetWindowsHookEx function fails.
if (hHook == 0)
{
  int err = Marshal.GetLastWin32Error();
  MessageBox.Show("SetWindowsHookEx Failed" + err.ToString());
  return;
}