PL/SQL :: Forming Number Type List In A Cursor?

we use oracle 11g. 11.2. I have a situation where in a pl-sql package, there is a modification needs to be done . Every User is associated with destination codes. For eg, user1==>0101,0104  There is a  destination_number and country field in the table1.Each of the destination number is associated with a country code and this combination is unique. for eg: 

dest_code   country_code 0101 CHINA 0202 UK 0101 Mexico 0104   Mexico 

For example, if user1 logs in to the system, then pl sql logic will look if that dest_code is in a table1,If the dest_code is present in the table1, then that dest_code number wont be added to the dest_code list formed for that user. For example,if user1 got dest_codes  0101,0104  associated with him.IF 0101 is in exception table then 0101 and 0104wont be used to form dest_code list. If NOT, a dest_code list will formed like 0101||0104. I am able to form the logic like I have a cursor that loops for each dest_code.For each dest_code , it will get that dest_code  into v_dest_code_no number type variable. open cursor fetch dest_code  no into v_dest_code  v_dummy number:=0;v_dest_code_list number:=0; LOOP v_dest_code_list:=v_dest_code ||v_dest_code ;  v_dest_code :=0; END LOOP:  How to make sure that for each dest_code set, if one of them is in table1, then the next number also will not be added to the list.