lib/createsend/list.rb
def update_custom_field_options(custom_field_key, new_options,
      keep_existing_options)
      custom_field_key = CGI.escape(custom_field_key)
      options = { :body => {
        :Options => new_options,
        :KeepExistingOptions => keep_existing_options }.to_json }
      put "customfields/#{custom_field_key}/options", options
    end
def update_custom_field_options(custom_field_key, new_options,
      keep_existing_options)
      custom_field_key = CGI.escape(custom_field_key)
      options = { :body => {
        :Options => new_options,
        :KeepExistingOptions => keep_existing_options }.to_json }
      put "customfields/#{custom_field_key}/options", options
    end
Updates the options of a multi-optioned custom field on this list.