• Nice summary here
• Example of waiting for a signal here
• An overview on capturing output from the app here

        retval =  _spawnl(_P_NOWAIT, "c:\\WINNT\\system32\\notepad.exe", "notepad", NULL);
        switch(retval)
        { case E2BIG:
               MessageBox( hWnd, TEXT("E2BIG!"), NULL, MB_OK);
               break;
        case EINVAL:
               MessageBox( hWnd, TEXT("EINVAL!"), NULL, MB_OK);
               break;
        case ENOENT:
               MessageBox( hWnd, TEXT("ENOENT!"), NULL, MB_OK);
               break;
        case ENOMEM:
               MessageBox( hWnd, TEXT("ENOMEM!"), NULL, MB_OK);
               break;
        }