Redmine

Hello everyone. I'm developing a plugin that should appear on the Redmine menu tab only when I'm inside Administration -> Users.
As of now, my init.rb is set to:

[code]
menu :application_menu, :costs, { :controller => 'costs', :action => 'index' }, :caption => 'Man Hour Costs'
[/code]

This shows the tab all the time if the user is not inside a project. I wanna limit this to be shown only when the user enters administration and click on Users - then it should appear as a tab. What should be the best way to do this?

Thanks!

PS - I don't want to make it appear on the administration page using :admin_menu =)