PLS-00103: Encountered the symbol "DECLARE" when expecting one of the following: begin function package pragma procedure subt

Hi,

i hava a following Trigger given below.It gives error anyone can solve my problem please.

CREATE or replace TRIGGER t_before_delete_on_Qdefs
BEFORE DELETE ON QDEFS
FOR EACH ROW
declare varTotEstTime number(12,2);
Declare CURSOR c IS Select A.Sserial,A.Qserial,QSetsum.TotEstTime, B.EstTime from QSetDet A,Qdefs B,QSetSum Where A.Qserial=B.Qserial and a.SSerial = QSetSum.SSerial and B.QSerial =:old.qserial Order By a.Sserial,a.QSerial;
DECLARE PRAGMA AUTONOMOUS_TRANSACTIONS;
BEGIN                  
            FOR J IN C LOOP
                if (J.TotEstTime > 0 and J.EstTime > 0) then  
               varTotEstTime:=J.TotEstTime-J.EstTime
               If varTotEstTime < 0 Then varTotEstTime = 0
                     update qsetsum set TotEstTime=varTotEstTime where SSERIAL=J.sserial;
                    DELETE FROM QSETDET WHERE  QSERIAL =:OLD.QSERIAL;
                    DELETE FROM QDefs_PList WHERE  QSERIAL =:OLD.QSERIAL;
        end if;    
            END LOOP;
EXCEPTION
   WHEN others THEN
        raise;
        END;
/
it will give error:

2/1      PLS-00103: Encountered the symbol "DECLARE" when expecting one of
         the following:
         begin function package pragma procedure subtype type use
         <an identifier> <a double-quoted delimited-identifier> cursor
         form current