If GET_LIST_ELEMENT_VALUE ('select_item',1) IS NULL Then
   DELETE_LIST_ELEMENT('select_item',1 );
   DELETE_LIST_ELEMENT('FEATURES.FEATURES', 1 );
End If; 

Add_List_Element('select_item', 
                (GET_LIST_ELEMENT_COUNT
                ('select_item')+1), 
                       :avail_item,
                       :avail_item); 

create table available(av_di varchar2(8),avail_item varchar2(25));

insert into available values('001','Arbor');
insert into available values('002','Fenced');
insert into available values('003','Electric Heating');

commit;