ASP.NET MVC ActionFilter parameter binding

If you have a model-bound parameter in an action method, how can you get to that parameter in an action filter?

[MyActionFilter]
public ActionResult Edit(Car myCar)
{
    ...
}

public class MyActionFilterAttribute : ActionFilterAttribute
{
    public void OnActionExecuted(ActionExecutedContext filterContext)
    {
        //I want to access myCar here
    }

}

Is there anyway to get myCar without going through the Form variables?