Help with a trigger

[jayjabour]

I tried this

CREATE OR REPLACE TRIGGER AXIUM."RMVBALTRG" 
BEFORE UPDATE OF
"LastPaymentAmount"
ON "PATIENT"
REFERENCING NEW AS NEW
FOR EACH ROW
DECLARE
v_bal NUMBER(10);
BEGIN
update  PTBAL_TMP set "Sum" = (Select sum("Sum" - :NEW."LastPaymentAmount" ) from ptbal_tmp where "Patient" = :NEW."Patient") where "Patient"= :NEW."Patient";
select "Sum" into v_bal from PTBAL_TMP where "Patient"=:NEW."Patient" ;
IF (v_bal <=0) THEN
update patient set  "Office1"=DECODE(trim("Office1"),'BAL',' ',"Office1"), 
                            "Office2"=DECODE(trim("Office2"),'BAL',' ',"Office2"), 
                            "Office3"=DECODE(trim("Office3"),'BAL',' ',"Office3"),
                            "Office4"=DECODE(trim("Office4"),'BAL',' ',"Office4"), 
                            "Office5"=DECODE(trim("Office5"),'BAL',' ',"Office5") where "Patient"=:NEW."Patient";
END IF;
exception
  when others then
    null;
END;
/

it compiles fine but doesn't do anything when I update the patient table.