mvc securityexception on action filter attribute

Question

So I have this security setup on my Action using the OnActionExecuting override of the ActionFilter Attribute.

public override void OnActionExecuting(ActionExecutingContext filterContext)
{
  RouteValueDictionary routeDeniedUsers = new RouteValueDictionary(new { controller = "Errorhandler", action = "NopeAintAllowed"});
 if(user.IsNotAllowed)
      throw new System.Security.SecurityException("You are not allowed to access page")
      return

 try{
///some process
}catch(SecurityException ex){
   if(ex != null)
        filterContext.Result = new RedirectToRouteResult(routeDeniedUsers);
}

}

so my question is, how do I display an error message to my "routeDeniedusers" Action once the users gets there? I would use TempData["key"] but visual studio only shows TempDataDictionary on the tool tip (or whatever you call that thing that shows the syntax). I would want to access the SecurityException instance but I odn't know how.

Should I really be using the SecurityException object in passing or should I use something else? Any advice is appreciated.

Thanks, G