Dynamic Master Pages in MVC

I have been working on a new project where I wanted to introduce the concepts of themes. This means that end users will be allowed to change the look and feel of the web application from a configuration menu. In order to deliver this functionality I needed to be able to dynamically change the master page on the fly. Since I am using MVC, I figured that there must be an event somewhere in the controller class that I can override to dynamically assign the master page. After a little bit of reading I discovered the OnActionExecuted event...