[marcoszorrilla]

Has probado algo así:

procedure TForm1.DBGrid1CellClick(Column: TColumn);
begin
  if DbGrid1.selectedIndex = 3 then
  begin
  DbGrid1.ShowHint:=True;
  DbGrid1.Hint:=Table1Titular.AsString;
  end
  else
  DbGrid1.ShowHint:=False;
end;

procedure TForm1.FormActivate(Sender: TObject);
begin
Application.HintColor:=clFuchsia;
Application.HintHidePause:=10000;
end;

Un Saludo.