can a trigger on insert -> update other tables?

i've got a "_rating" table that, when a new record is added,
i'd like to have propagate through some other tables to update
running totals:

CREATE FUNCTION _rating_propagate( _rating ) RETURNS OPAQUE AS '
DECLARE

n ALIAS FOR $1;
opinion char(1) := upper(substring(n.rating from 1 for 1));

BEGIN

UPDATE sometable SET fld = fld + 1 WHERE id = .... ;
UPDATE othertable SET fld = fld + 1 WHERE id = .... ;
[yada yada]
END;
' LANGUAGE 'plpgsql';

CREATE TRIGGER _rating_propagate
BEFORE INSERT ON _rating
FOR EACH ROW EXECUTE PROCEDURE _rating_propagate( NEW );

INSERT INTO _rating VALUES ( ... );

the insert into _rating works fine, but none of the other tables
are actually UPDATED. who's got the clue stick?

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