Раскрывающийся список в StringGrid

На форму кладем StringGrid, ComboBox и SpeedButton.

procedure TForm3.StringGrid1SelectCell(Sender: TObject; 
    ACol, ARow: Integer; var CanSelect: Boolean);
var R : TRect;  
begin    
  if ((ACol = 1) AND (ARow <> 0)) then begin  
    //Вставка ComboBox (delphikingdom) во 2-й стобец
    R := StringGrid1.CellRect(ACol, ARow);
    R.Left  := R.Left + StringGrid1.Left;
    R.Right := R.Right + StringGrid1.Left;
    R.Top := R.Top + StringGrid1.Top;
    R.Bottom := R.Bottom + StringGrid1.Top;
    ComboBox4.Top := R.Top + 1;
    ComboBox4.Left := R.Left + 1;
    ComboBox4.Width := (R.Right + 1) - Kvadr.Left;
    ComboBox4.Height := (R.Bottom + 1) - Kvadr.Top;
    ComboBox4.Visible := True;
    ComboBox4.SetFocus;
    SpeedButton3.Visible := False;
  end
  else if ((ACol = 2) AND (ARow <> 0)) then begin 
    //Вставка SpeedButton в 3-й стобец
    ComboBox4.Visible := False;          
    R: = StringGrid1.CellRect(ACol, ARow);
    SpeedButton3.Top := R.Bottom - SpeedButton3.Height - 1;
    SpeedButton3.Left := R.Right - SpeedButton3.Width - 1;
    SpeedButton3.Parent := StringGrid1;
    SpeedButton3.Visible := True;
  end
  else begin 
    ComboBox4.Visible := False;
    SpeedButton3.Visible := False;
  end;
  CanSelect := True;
end;