Pegar valor antigo em um UPDATE

try
  with DataModulo.Query do
  begin
    if (Active) then
      Close;
    SQL.Clear;
    SQL.Add('UPDATE PARCELAS SET VALOR = :VALOR WHERE ID = :ID RETURNING (OLD.VALOR)');
    ParamByName('ID').AsInteger := AID;
    ParamByName('VALOR').AsCurrency := AValor;
    Open;
    auxValorAntigo := FieldByName('VALOR').AsCurrency;
  end;
  DataModulo.Transaction.Commit;
except
  on E: Exception do
  begin
    DataModulo.Transaction.Rollback;
    raise Exception.Create('Erro ao alterar o valor da parcela!' + #13 + E.Message);
  end;
end;