Error handleing with redirect_to

I'm sketching out a error handler, something like

if cando = false    redirect_to( :controller => Oops,                 :action => 'accessdenied',                 :type => 'alarm',                 :message => 'no_permission_to_view',                 :return_to => saved_url,    ) else .... end

Is this an internal redirection or does it immedate send that url to the browser as

             http://mysite.com/Oops/accesdenied?type=alarm+

What I want is the message sent to the user with a view custom for the action parameter. It would be nice it if it was a popup rather than a whole new page, but I'll live with that.

Am I on the wrong track here? I seem to be getting problems with routing.