How to change Page Read only on runtime in Oracle APEX

Make process to change Page Read only on runtime

BEGIN

UPDATE APEX_200200.wwv_flow_steps -- PageS

SET READ_ONLY_WHEN_TYPE = 'EXISTS' ,

READ_ONLY_WHEN = 'select 1 from dual where 1=1'

WHERE FLOW_ID = :P7_FLOW_ID -- APP ID

 and ID = :P7_STEP_ID  -- PAGE ID

; 

end;

--
thanks