Mini Media Player, versione corretta!

#include <WindowsConstants.au3>
#include <GuiConstants.au3>
#include <ButtonConstants.au3>
#include <Sound.au3>
TrayTip("Welcome","Hi! Welcome My Media Player!",5)

GUICreate("Mini Media Player", 300,100)
GUISetBkColor(0x7FD4FF)
GUICtrlCreateLabel("Welcome a Mini Media Player!",2,2)
GUISetBkColor(0x7FD4FF)
$play = GUICtrlCreateButton("Play",150,50)
$Pause = GUICtrlCreateButton("Pause", 110,50)
$Stop = GUICtrlCreateButton("Stop",180,50)
$apri = GUICtrlCreateButton("Open file",5,50)
$durata = GUICtrlCreateLabel("Durata: 00:00:00 / 00:00:00",1,30)
$volume = GUICtrlCreateLabel("Volume:",150,30,100,20)
$slider = GUICtrlCreateSlider(180,0,80,30)
GUICTRlSetBkColor($slider,0x7FD4FF)
GUISetState(@SW_SHOW)
$4 = ''
While 1
       $vol = 100 - GUICtrlRead ($slider)
   SoundSetWaveVolume ($vol)
       GUICtrlSetData ($volume,"Volume: "&$vol)
       GUICtrlSetData($durata,"Durata: "&_SoundLength($4)&" / "&_SoundPos($4))
      $msg = GUIGetMsg()
      Switch $msg
      Case $apri
                $4 = FileOpenDialog("Open Sound",@DesktopDir,'Music Files(*.mp3;*.wma;*.midi;*.wav)')
                _SoundPlay($4)
      Case $play
              _SoundPlay($4)
      Case $stop
              _SoundStop($4)
      Case $pause
              _SoundPause($4)
      Case $Gui_event_close
              Exit
              EndSwitch
      WEnd