pl/pgsql question

I have created a function in pl/pgsql to modify a row before it gets put
into the database, but it seems my modification is being ignored, and
the unmodified row is being inserted.

I have confirmed with this RAISE EXCEPTION that my "NEW" row is modified
properly, however it is not being stored in the db.

NEW.start_date := NEW.start_date+delta;
-- RAISE EXCEPTION ''new start date: % '',NEW.start_date;
NEW.end_date := NEW.end_date+delta;

It's probably something very obvious, but I'm mystified.

Tim

--
-- Function to enforce dependencies in the table structure
--
CREATE OR REPLACE FUNCTION projtask_insert_depend () RETURNS OPAQUE AS '
DECLARE
dependent RECORD;
delta INTEGER;
BEGIN
--
-- First make sure we start on or after end_date of tasks
-- that we depend on
--
FOR dependent IN SELECT * FROM project_depend_vw
WHERE
project_task_id=NEW.project_task_id LOOP
--
-- See if the task we are dependent on
-- ends after we are supposed to start
--
IF dependent.end_date > NEW.start_date THEN
delta := dependent.end_date-NEW.start_date;
-- RAISE EXCEPTION ''delta: % '',delta;
NEW.start_date := NEW.start_date+delta;
-- RAISE EXCEPTION ''new start date: %
'',NEW.start_date;
NEW.end_date := NEW.end_date+delta;
END IF;

END LOOP;
RETURN NEW;
END;
' LANGUAGE 'plpgsql';

CREATE TRIGGER projtask_insert_depend_trig AFTER INSERT ON project_task
FOR EACH ROW EXECUTE PROCEDURE projtask_insert_depend();