ScrollBox automatikus görgetése kör alakban

procedure TForm1.Timer1Timer(Sender: TObject);
…

  ax:=ScrollBox1.HorzScrollBar.Range div 4;
  ay:=ScrollBox1.VertScrollBar.Range div 4;

  x:=Round(cos(DegToRad(FI))*ax+ax);
  y:=Round(sin(DegToRad(FI))*ay+ay);
…

  SendMessage(ScrollBox1.Handle, WM_VSCROLL, SB_THUMBPOSITION+x*65536, 0);
  SendMessage(ScrollBox1.Handle, WM_HSCROLL, SB_THUMBPOSITION+y*65536, 0);
  inc(FI);
end;