Оштбка TTrackBar DoMouseWheel

 TTrackBar = class(ComCtrls.TTrackBar)
  protected
    function DoMouseWheel(Shift: TShiftState; WheelDelta: Integer; MousePos: TPoint): Boolean; override;
  end;
 
function TTrackBar.DoMouseWheel(Shift: TShiftState; WheelDelta: Integer; MousePos: TPoint): Boolean;
begin
  Position := Position + WheelDelta div 30;
  Result := True;
end;

в formcreate другой формы, но почему ошибка?
for i := 3 to 12 do
  begin
   [B] with findcomponent('TrackBar'+IntToStr(i))as ttrackbar do[/B]
      handle1:=handle;
    SetWindowLong(handle1, GWL_USERDATA,SetWindowLong(handle1, GWL_WNDPROC, LPARAM(@MyTrackBarProc)));
  end;