EXECUTE USING problem

Using PG 9.0.3, I wish to dynamically reference a column in a table
passed into a PL/PgSQL function as follows:

-- A table with some values.
DROP TABLE IF EXISTS table1;
CREATE TABLE table1 (
code INT,
descr TEXT
);

INSERT INTO table1 VALUES ('1','a');
INSERT INTO table1 VALUES ('2','b');

-- The function code.
DROP FUNCTION IF EXISTS foo (TEXT);
CREATE FUNCTION foo (tbl_name TEXT) RETURNS VOID

AS $$
DECLARE
r RECORD;
d TEXT;
BEGIN
FOR r IN
EXECUTE 'SELECT * FROM ' || tbl_name
LOOP
--SELECT r.descr INTO d; --IT WORK
EXECUTE 'SELECT ($1)' || '.descr' INTO d USING r; --DOES NOT WORK
RAISE NOTICE '%', d;
END LOOP;

END;
$$ LANGUAGE plpgsql STRICT;

-- Call foo function on table1
SELECT foo('table1');

Another post suggested EXECUTE 'SELECT $1::text::table1.descr' INTO d
USING r; but this does not work either. Can this be achieved currently?
what would be the syntax ?

Thanks in advance.