#include <GUIConstantsEx.au3>
#include <WindowsConstants.au3>
Global $hGui, $iW = 350, $iH = 200, $iWl = 100, $nLabel, $iHl = 80
$hGui = GUICreate('Test', $iW, $iH, -1, -1, $WS_OVERLAPPEDWINDOW)
$nLabel = GUICtrlCreateLabel('', Int($iW - $iWl) / 2, Int($iH - $iHl) / 2, $iWl, $iHl)
GUICtrlSetBkColor(-1, 0x0000FF)
GUISetState()
GUIRegisterMsg($WM_SIZE, 'WM_SIZE')
Do
Until GUIGetMsg() = $GUI_EVENT_CLOSE
Func WM_SIZE($h_Wnd, $i_Msg, $i_wParam, $i_lParam)
#forceref $i_Msg, $i_wParam
Local $i_W, $i_H
$i_W = BitAND($i_lParam, 0xFFFF)
$i_H = BitShift($i_lParam, 16)
GUICtrlSetPos($nLabel, Int($i_W - $iWl) / 2, Int($i_H - $iHl) / 2, $iWl, $iHl)
Return $GUI_RUNDEFMSG
EndFunc ;==>WM_SIZE