About EXECUTE in pl/pgsql

Hi, 
I do following in pl/pgsql. (st1 has been set to "LIKE 'abc%' ")
EXECUTE ''CREATE TEMP TABLE comuser AS '' || ''SELECT * FROM comt_user1 WHERE username ''||St1|| ''ORDER BY
username;'';

I've got "ERROR: EXECUTE ..SELECT INTO hasn't impletmented", How can??

JACK