Dynamic datalogging function/scheme

Hello,

Looking for advice on creating as dynamic a datalogging scheme as I can
using plpgsql.

The idea would be to have a trigger function that I could drop on any
table in my database. Then on update, the function would iterate
through each field, and check to see if NEW.<fieldname> <>
OLD.<fieldname>. Then a function would be called that would insert
data into a logging table.

I can do this in a very static sense whereby each table has its own
specific trigger function that specifies each column by name
(NEW.co_name <> OLD.co_name), etc. But, this is pretty cumbersome, and
as new columns are added, we would need to remember to go in and change
the function.

Running Postgresql 8.1

Thanks for any advice/help!