Procedure check_data(block_name in varchar2)
First_item varchar(20);
Current_item varchar(20);
Last_item varchar(20);
Begin
First_item := get_block_property(block_name, FIRST_ITEM);
Last_item := get_block_property(block_name, LAST_ITEM);
Current_item := first_item;
Loop
    If value_of(current_item) is null then
        Message(current_item); pause;
    End if;
Exit when current_item = last_item;
Current_item := the_item_after(current_item);
End loop;
End;