update in rule

Hello.

We are running PostgreSQL 7.1.3 on Debian GNU/Linux.
We maintain for our intranet something like an addressbook :

<base>=# \d adresses
Table "adresses"
Attribute | Type | Modifier

--------------+------------------------+----------------------------------------
id | integer | default nextval('adresses_id_seq'::text)
<snip>
date_maj | date | default 'NOW'
Index: adresses_pkey

I would like to automatically update the `date_maj' field with the
current day date whenever an update on a row occurs.

So I created a rule like :

CREATE RULE adresses_date_maj
AS ON UPDATE TO adresses
DO UPDATE adresses SET date_maj = 'NOW' ;

But as says the documentation, this does not work (circular problem).

Does anyone known how to achieve such a behaviour ?

Thanks in advance,
Nicolas.