Trigger from a function

Hello all,

I have a problem with a trigger which is executed when i make an UPDATE trought a simple query, but
not when the UPDATE is made in a store procedure.

Maybe i'm missing something in the declaration of the function and i would appreciate any help.
T
his is the function:

CREATE OR REPLACE FUNCTION X
  RETURNS SETOF void AS
$BODY$

begin
  update A;
end;
$BODY$
  LANGUAGE 'plpgsql' VOLATILE;


The trigger:

CREATE TRIGGER Y
  BEFORE INSERT OR UPDATE
  ON A
  FOR EACH ROW
  EXECUTE PROCEDURE Z;

CREATE OR REPLACE FUNCTION Z
  RETURNS "trigger" AS
$BODY$
begin
     if (tg_op in ('INSERT', 'UPDATE', 'DELETE')) then
        update A;
     end if;
$BODY$
  LANGUAGE 'plpgsql' VOLATILE;


Thanks in advance.
Danilo Guevara
Departamento de Sistemas
Acceso Crediticio SAC