function that return multiple fields and rows

Hi All,
I would like to write a function that returns multiple rows and multiple
fields, something like this. I know the syntax is probably wrong, any helps
would be appreciated.

CREATE FUNCTION GetGuestbookMessages (int4) RETURNS SETOF VARCHAR AS
'
SELECT guestname, guestemail FROM GuestbookMessages WHERE UserId = $1
' LANGUAGE 'sql';

notice that I want to return more than one field and more than one record in
the above function. Thanks.

wooi.