Howto automatically define collumn names for a function result.

Hi,
wouldn't it be great to have functions return  "setof something" as 
result where "something" was determined out of the result of a SELECT 
within the function?
like

CREATE OR REPLACE FUNCTION coffee(integer, timestamp, timestamp) RETURNS SETOF
AS
$BODY$   SELECT staff_id, name, room, COUNT(coffee_id) AS cupcount    FROM staff  JOIN coffee_log ON staff_fk =
staff_id   WHERE (staff_id = $1) AND (coffee_time BETWEEN $2 AND $3) GROUP BY staff_id, name, room ORDER BY name;
 
$BODY$ LANGUAGE 'sql' STABLE

There the SELECT dumps a constant set of collumns where as far as I know 
have to be defined as a type to make SETOF happy or define the names 
whenever I call the function which would be tedious.

Actually this is a pretty simple example of some reports I need to produce.
They have around 60 collumns and there is also an aggregate and 
filtering on an id as well as 2 timestamps.
Since the aggregate depends on id and timestamps too, it is no solution 
to build a view and select from that within the function.