SQL Caching and Entity Framework

I have put together a small ASP.NET MVC 2 site that does some very extensive date mining/table-joins/etc.

Using MVC, I have a controller that returns the data in many different forms (tables, images, etc). To save hitting the database frequently I have a dual cache mechanism:

1. For identical parameters to the same action I use the OutputCacheAttribute with VaryByParam = "*".
2. Assuming some parameter to the action has changed (or another action is called), it is still possible that my "data" has previously been requested, so I store the data in a view model after the first hit of the database, I achieve this with a .NET 4.0 System.Runtime.Caching.ObjectCache.

Example of the ObjectCache inside of the Controller:

private static readonly ObjectCache cache = 
      new MemoryCache("CompareControllerCache");
private static void CacheObject(ViewModel obj, 
                                string param1, 
                                int someOtherParam )
{
    string key = string.Format("{0}-{1}", param1, someOtherParam);
    Trace.WriteLine(string.Format("Adding {0} to the cache", key));
    cache.Add(key, obj, new CacheItemPolicy
         {
             SlidingExpiration = TimeSpan.FromMinutes(1)
         });
}

// Corresponding GetCachedObject with similar key defining logic.

This gives me a good performance improvement, but where it fails is on the CacheItemPolicy being very simple. Ideally, I'd like the cache-window to be bigger but have the cached item expire if the database changes.

The CacheItemPolicy seems to support this with the ChangeMonitors collection, to which I could add a SqlChangeMonitor, but when trying to construct this is where I come to a halt.

I am using Entity Framework 4 to access an SQL Database, how how do I construct the SqlChangeMonitor to monitor the couple of database tables that are likely to trigger a cache expire?

SqlChangeMonitor is constructed with an SqlDependency which takes an SqlCommand - how can I latch upon Entity Framework's encapsulation of my database?