AutoCAD Inventor :: Extract Rev Of A Model (part Or Assembly) From Drawing

I'm trying to extract the Rev of a model (part or assembly) from a drawing.  Since Inventor has independent revs for the model and idw I am trying to drill down and put the rev from the model referenced.  I got it to work for ipts and many iams using:

Dim oModelDoc As Document
Set oModelDoc = oDocument.Sheets(1).DrawingViews(1).ReferencedDocumentDescriptor.ReferencedDocument

The problem I have is when the drawing only references an ipn presentation file.  The ipn ALSO has it's own independant rev!  I'm trying access the model the ipn references but cannot get it to work.

BTW, I do know about the ability to sync idw and ipt properties.  I have enable it for our template but we have a lot of legacy drawings that don't have this option selected.  I also haven't tested that method with an drawing that only references an ipn.

Code is below with offending section in bold:

' Find model (part or assembly) referenced by drawing if active document is a drawing
If oDocument.DocumentType = kDrawingDocumentObject Then
Dim oModelDoc As Document
Set oModelDoc = oDocument.Sheets(1).DrawingViews(1).ReferencedDocumentDescriptor.ReferencedDocument

[Code]....