Global MyOldList.l
Declare ListCB(hWnd.l, Message.l, wParam.l, lParam.l)
Declare GetListColumnClicked()

Procedure ListCB(hWnd.l, Message.l, wParam.l, lParam.l)
  Protected *Header.HD_NOTIFY
  Protected Result.l=CallWindowProc_(MyOldList.l, hWnd.l, Message.l, wParam.l, lParam.l)
  Select Message.l
    Case #WM_NOTIFY
    *Header=lParam.l
    If *Header\hdr\code=#HDN_ITEMCLICK
       ListCB_Column_Clicked.l=*Header\iItem
       MessageRequester("","Spalte "+Str(ListCB_Column_Clicked.l)+" wurde geklickt.",0)
    EndIf
  EndSelect
  ProcedureReturn Result.l
EndProcedure

If OpenWindow(0,0,0,500,250,"Window",#PB_Window_SystemMenu|#PB_Window_ScreenCentered)
  ListIconGadget(1,10,10,480,230,"Spalte 0",100,0)
  AddGadgetColumn(1,1,"Spalte 1",100)
  AddGadgetColumn(1,2,"Spalte 2",100)
  
  MyOldList.l = SetWindowLongPtr_(GadgetID(1),#GWL_WNDPROC,@ListCB())
Repeat : Until WaitWindowEvent() = #PB_Event_CloseWindow
EndIf