ApplicationController Plugin

I've created a plugin to generate error pages with a single function
call. The basic idea is that in your action you could call
error_forbidden and an error page would be rendered with the HTTP
status code 402. This works great so far when called from within an
action, but when I want to add the call to the "verfy" line, things

verify :method => :post, :only =>
[ :create, :update, :destroy ], :render => { :text => error_invalid }

Generates the error message: "undefined method `error_invalid' for

How can I make the methods visible to the controller outside the
actions? For some reason I haven't been able to make it work for
both. Here's a snippet from the plugin:

# ErrorPage
module ErrorPagePlugin