Mocking a Using with a FileStream

I have been trying to mock out a using with a file stream but have not been able to complete this and am unsure how to do it, I am using rhino mock.

private Connection LoadConnectionDetailsFromDisk(string bodyFile)
{     
   //logic before
   using (FileStream fs = File.Open(bodyFile, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
   {
     return this.serverConfiguration.LoadConfiguration(fs, flowProcess);
   }
    //more logic
}

Could anyone tell me how to mock the using(FileStream....) so I am able to access this branch of the code?