Trigger problem

Hi guys

Im tryint to make a trigger that marks a tuble as changed whenever someone
has updated it

my table looks something like this

create table myTable (   ...   changed boolean;
)

now ive been working on a trigger and a sp that looks like this, but it
doesnt work...

create function myFunction returns trigger as '   begin       new.changed = true;       return new;   end;
' language 'plpgsql';

create trigger myTrigger
after update on lektioner
for each row
execute procedure myFunction();


the code compiles, runs, and doesnt whine about anything, but nothing
changes...

any ideas??

- Kasper