iterating over all NEW.* values in a trigger?

Inside a plpgsql function trigger, is it possible to a loop over all
fields of the NEW record (and inspect their value) without knowing in
advance from which table NEW will come?

I am trying the following:

DROP FUNCTION arch_func();
CREATE FUNCTION arch_func() RETURNS opaque AS '
DECLARE
    rec ecord;
BEGIN
    FOR rec IN SELECT a.attname,t.typname FROM pg_attribute a JOIN pg_class c
            ON (a.attrelid = c.oid AND c.relname = TG_RELNAME) JOIN pg_type t
            ON (t.oid = a.atttypid) LOOP
        RAISE NOTICE ''Hello %: %!'', rec.attname, rec.typname;
        --
        -- here I would like to access NEW.rec.attname in order to be able
        -- to:
        -- 1) compare it to OLD.rec.attname,
        -- 2) check if there is a change,
        -- 3) save a changed value in another "archive" table
        --
    END LOOP;
    RETURN NULL;
END;
' LANGUAGE 'plpgsql';

DROP TRIGGER arch_after ON auction;
CREATE TRIGGER arch_after AFTER UPDATE OR DELETE ON auction FOR each ROW EXECUTE PROCEDURE arch_func();

--
    PHEDRE: Dans mes jaloux transports je le veux implorer.
            Que fais-je ? O� ma raison va-t-elle s'�garer ?
                                          (Ph�dre, J-B Racine, acte 4, sc�ne 6)