This code will get the description of the attached model file of all open drawings.
Dim oDoc As Document
For Each oDoc In ThisApplication.Documents.VisibleDocuments
AttachedModel = oDoc.Sheets.Item(1).DrawingViews.Item(1).ReferencedDocumentDescriptor.ReferencedDocument
Description = AttachedModel.PropertySets.Item("Design Tracking Properties").Item("Description").Value
Next