Redmine

New to Redmine and Ruby and I have a question, where would I fix the hook code that is called here:

issues_helper.rb: 283

call_hook(:helper_issues_show_detail_after_setting,
              {:detail => detail, :label => label, :value => value, :old_value => old_value })

Where is the helper_issues_show_detail_after_setting class?

Thanks...