Oracle Forms

I am using Forms 10g.

i am writting a procedure in When mouse double click trigger that will display all the values available for ip address from this procedure.

The procedure is
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DECLARE
CURSOR cr
IS
SELECT LEVEL NUM
FROM DUAL
CONNECT BY LEVEL<=(Select max_range from t_ip_address_dtl where category_name=:t_item_cpu.category and block_name =:block_head.block)
MINUS
SELECT TO_NUMBER(SUBSTR(IP_address, 12))
FROM T_item_cpu;
abc number(4);
abc1 number(4):=null;
BEGIN
FOR rec IN cr LOOP
abc1 := abc1 || ',' || rec.num;
END LOOP;
Message('You can use between these nos: '||abc1);
Message('You can use between these nos: '||abc1);

END;


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It is showing this error :-