SQL & PL/SQL

Hi,
I have the requirement to run job daily at particular time with out deleting current job from scheduler, can we alter in oracle scheduler job interval for the job with out creating new job.I am adding code,
for daily:repeat_interval => 'FREQ=daily;byhour=19;byminute=00;bysecond=00',

this is actual code

BEGIN
DBMS_SCHEDULER.create_job
(job_name => 'employee_mv_job_dblink',
job_type => 'PLSQL_BLOCK',
job_action => 'begin employee_mv_refresh@dblink;commit;end;',
start_date => SYSTIMESTAMP,
repeat_interval => 'FREQ=minutely;interval=1',
enabled => TRUE,
comments => 'Gather table statistics'
);
END;

thanks in advance
Ganesh