Pnrdba,

There has been a typo in Julian's message that you have addopted in all of your following tries. There should be two single quote characters around SUNDAY, before and after it. In Julian's message there are two single quotes before and two double quotes after the name of the day. So the following should work for you (if you have NLS_LANGUAGE set to AMERICAN):
Code:
begin
  DBMS_JOB.SUBMIT(:jobno, 'CALL_WEEKLY;',
  sysdate,
  'NEXT_DAY(TRUNC(SYSDATE),''SUNDAY'')+3/24');
end;
/