calculated default

["SunWuKung" <Balazs.Klein@xxxxxxxxxxx>]

I have a table with a sequence as its primary key.
On insert I would like to have all its fields (except the primary key)
default to the last one in the table (order by id desc limit 1).
I guess I should use a trigger to do this but I don't know how.

Thanks for the help.
SWK