function CF_3MONTHSPLUSFormula return Number is
	V 		NUMBER(20) ;
	VBILL NUMBER(20) ;
	VTIP  NUMBER(20) ;
	VAMT  NUMBER(20) ;
begin

	SELECT SUM(AMOUNT)
	  INTO VBILL
	  FROM BILLDETAIL
	 WHERE BILLMTRNO IN (SELECT BILLMTRNO 
	 											 FROM BILLMASTER
	 											WHERE BILLDATE < TRUNC(ADD_MONTHS(:PBILLMONTH, -3), 'MONTH')) 
	   AND BILLMTRNO NOT IN (SELECT NVL(BILLMTRNO, 0)
	                           FROM ACCOUNT3) ;

	SELECT TIPAMOUNT 
	  INTO VTIP 
	  FROM BILLMASTER
	 WHERE BILLMTRNO IN (SELECT BILLMTRNO 
	 											 FROM BILLMASTER
	 											WHERE BILLDATE < TRUNC(ADD_MONTHS(:PBILLMONTH, -3), 'MONTH')) 
	   AND BILLMTRNO NOT IN (SELECT NVL(BILLMTRNO, 0)
	                           FROM ACCOUNT3) ;
	 
	VAMT := NVL(VBILL, 0) + NVL(VTIP, 0) ;
	
	RETURN VAMT ;
	
EXCEPTION
	WHEN NO_DATA_FOUND THEN
	RETURN NULL ;
	WHEN OTHERS THEN
	RETURN NULL ;
end;