How do you create a Boxed Return or Cornice Return?

[rgecy]

I have a 10/12 roof with gables. How do you create the boxed return on the gable end? I have used the Hot Sweep to add the fascia but I am left with the opening between my fascia and soffit. Any suggestions? Where do I start?

I have included an example revit file of my problem.

Thanks,
Robert