Here is an example:
#include <Constants.au3>
#include <GUIConstantsEx.au3>
#include <SendMessage.au3>
#include <SliderConstants.au3>
#include <WinAPI.au3>
#include <WindowsConstants.au3>
#include <StructureConstants.au3>
Global Const $tagNMCUSTOMDRAW = 'hwnd hWndFrom;uint_ptr IDFrom;int Code;dword DrawStage;hwnd hDC;' & $tagRECT & ';dword_ptr ItemSpec;uint ItemState;lparam ItemlParam'
Global Const $STM_GETIMAGE = 0x0173
Global $hGui = GUICr