PL/SQL question

Hello everyone,

I try to see if i can make a recursive function with a trigger set on
INSERT and doing an insert under my trigger function.

So i wrote a test function :

CREATE OR REPLACE FUNCTION testfunc() RETURNS SETOF RECORD AS '
DECLARE
use_t RECORD;
BEGIN

SELECT INTO use_t id_categorie FROM categorie ORDER BY id_categorie
DESC;
IF use_t.id_categorie<>50 THEN
INSERT INTO categorie (nom) VALUES (''test'');
END IF;

RETURN NULL;

END;
'LANGUAGE plpgsql;

The problem is that i can't exec this function to test it, psql return
the following error :

"ERROR: set-valued function called in context that cannot accept a set"

But my INSERT INTO works if i write it directly.

Someone get an idea ?

Thx in advance,
regards,