declare
  counter number := 0;  -- not 1 for the case of empty block
begin
  first_record;
  while :system.last_record = 'FALSE'
  loop
    counter := counter + 1;
    next_record;
  end loop;

  if counter > 0 then
     counter := counter + 1;  -- the last record was not counted
  end if;
  
  message('There are ' || to_char(counter) || ' records in the block');
end;