Rails - Dec 2005 - Calling helper from a controller

I try to call a helper define inside the *application_helper.rb* but I 
obtain an error.
Is it possible ?
There is an other way ?

Thanks

<%if @troll.nil? %>
> I try to call a helper define inside the *application_helper.rb* but I
> obtain an error.
Error text dump please.
> Is it possible ?
Ever
> There is an other way ?
mappy.fr ?