# File lib/spreadsheet/excel/offset.rb, line 17
        def offset *keys
          keys.each do |key|
            attr_reader key unless instance_methods.include? key.to_s
            define_method "#{key}=" do |value|
              @changes.store key, true
              instance_variable_set "@#{key}", value
            end
            define_method "set_#{key}" do |value, pos, len|
              instance_variable_set "@#{key}", value
              @offsets.store key, [pos, len]
              havename = "have_set_#{key}"
              send(havename, value, pos, len) if respond_to? havename
            end
          end
        end