/* Formatted on 10/4/2013 4:02:34 PM (QP5 v5.240.12305.39476) */
SELECT CASE
WHEN TO_CHAR (TO_DATE (SYSDATE, 'dd/mm/yyyy'), 'DAY') = 'MONDAY'
THEN
SYSDATE + 4
WHEN TO_CHAR (TO_DATE (SYSDATE, 'dd/mm/yyyy'), 'DAY') <> 'MONDAY'
THEN
SYSDATE - 1
END
expected_date
FROM DUAL;