Expiring action from outside the controller

Hi all,

I have a drb process that performs some data insertions which should
result in expiring an action cache in one of my controllers.

Does anyone know how to do this? I tried instantiating a new instance
of the controller and expiring the action like this (in a helper):

controller = MyController.new
controller.expire_action(:action=>‘users_list’, :id=>auser.user_name)

But when I make that call I get the following exception:

You have a nil object when you didn’t expect it!
The error occured while evaluating nil.rewrite

Any ideas?