Is there any problem extend ApplicationHelper in application controller

Hi
  I have a function in ApplicationHelper say an example

def url_needed
  if current_user.is_staff?
    home_url
  else
    another_url
  end
end

And in ApplicationController what I did is

   def check_for_the_feature
       flash[:notice] = 'You have no permission to do this.'
       self.extend ApplicationHelper
       redirect_to url_needed
   end

Is there any problem extending helper like this.

Thanks