🚀 go-pugleaf

I'm trying to have my program detect that another instance is running, 
send a "Show" message to the already running instance, and then return. 
I'm using Builder 6.

It appears that I always get a non null mutex so the message is never 
sent.  Here's some code.

Thanks

UINT WM_MYMSG;
HANDLE CheckForInstance(const UINT WM_MYMSG);

<snip>
WINAPI WinMain(HINSTANCE, HINSTANCE, LPSTR, int)
{
         HANDLE mutex;
         try
         {
                  String sTitle = "Google Earth (C) Tool";
                  String sMessage = 
"USDA.FS.FireScience.GooleEarthTool.Awake";
                  Application->Title = sTitle + " Temporary";
                  WM_MYMSG = RegisterWindowMessage(sMessage.c_str());
                  if((mutex = CheckForInstance(WM_MYMSG)) == NULL)
                     return 0 ;    //  second instance
                  Application->Title = sTitle;
                  Application->Initialize();
                  Application->CreateForm(__classid(TFormMain), &FormMain);
                  Application->CreateForm(__classid(TAboutBox), &AboutBox);
                  Application->Run();
         }
</snip>

//---------------------------------------------------------------------------
HANDLE CheckForInstance(const UINT WM_MYMSG)
{
   SetLastError(0) ;
   char * m_Name = "USDA.FS.FireScience.GooleEarthTool";
   HANDLE m_Handle = CreateMutex(NULL, false, m_Name);
   if(m_Handle != NULL)
     return m_Handle;      // this is the first instance
   if(GetLastError() == ERROR_ALREADY_EXISTS)
     PostMessage(HWND_BROADCAST, WM_MYMSG, NULL, NULL);
   return NULL;     //  NULL handle
}


<snip>
        if (mutex != NULL)
            ReleaseMutex(mutex);
</snip>

-- In TFormMain

//----------------------------------------------------------------------------
void __fastcall TFormMain::WndProc(TMessage& message)
{
    if(message.Msg == WM_MYMSG)
      FormMain->Show();
    else
       TForm::WndProc(message); //pass on to parent
}