#include <ComboConstants.au3>
#include <GuiComboBoxEx.au3>
#include <GUIConstantsEx.au3>

$hGUI = GUICreate("", 200, 40)
$Combo = GUICtrlCreateCombo("item1", 10, 10, 180, 100, BitOR($CBS_DROPDOWNLIST, $CBS_AUTOHSCROLL))
GUICtrlSetData(-1, "item2|item3", "item3")
GUISetState()

While 1
    Switch GUIGetMsg()
        Case $GUI_EVENT_CLOSE
            Exit
        Case $Combo
            MsgBox(262144, "Test", "Index = " & _GUICtrlComboBoxEx_GetCurSel(GUICtrlGetHandle($Combo)))
    EndSwitch
WEnd