map static files to alternate path

So I have a MVC website at this location on disk: C:\MyApp\Applications\1.0.0.0, however I have static resources in a shared location like: C:\OtherApps\myapp\css\site.css

How can I intercept requests for static files to my MVC app and map the path to this alternate resources location? I have an IHttpHandler that I can apply to specific paths, but I want to do this for all static files (things that don't match an MVC route).

note: nothing is serving resources from the alternate location, so a rewrite will not work.