Throwing Chttpexception Problem

dear all,

i found that throwing an CHttpException doen't show the site/error page.
is there any solution to force the application to show the error page with a specific exception,.?

one more question,
there is an on going project with modules to divide functionality.
i am responsible to handle the authorization to each user's action.
is it possible to implement RBAC without change every contoller file,.?
i have been thinking to do the authorization inside the beforeAction method. any idea,.?

thanks