Decoding   (28.07.08 15:40) [4]

type
 TLabelArrEx = class(TControl)
 private

   PrevParentWndProc: Pointer;

   procedure NewParentWndProc(var Msg: TMessage);
 public
   constructor Create(AOwner: TComponent); override;
 end;

constructor TLabelArrEx.Create(AOwner: TComponent);
var
 p: Pointer;
begin
 inherited Create(AOwner);

 PrevParentWndProc:=Pointer(GetWindowLong(TScrollBox(Owner).Handle, GWL_WNDPROC));
 p:=MakeObjectInstance(NewParentWndProc);
 SetWindowLong(TScrollBox(Owner).Handle, GWL_WNDPROC, LongInt(p));
end;

procedure TLabelArrEx.NewParentWndProc(var Msg: TMessage);
begin
 Msg.Result:=CallWindowProc(PrevParentWndProc, TScrollBox(Owner).Handle, Msg.Msg, Msg.WParam, Msg.LParam);

 case Msg.Msg of
   wm_size: DoSomething
  end;
end;