I needed to trace the boundaries of Architectural Spaces, and the best I could come up with is collecting the object snap points, specifically the end points. This is what I did, I'd think you could to the same with a wall.
Dim mySpace As Autodesk.Aec.Arch.DatabaseServices.Space = SpaceId.GetObject(OpenMode.ForRead)
Dim pickPT As Point3d
Dim myPlPtColl As New Point3dCollection
Dim geomlds = New IntegerCollection(1)
geomlds.Add(0)
mySpace.GetObjectSnapPoints(ObjectSnapModes.ModeEnd, 0, pickPT, pickPT, Matrix3d.Identity, snapPts, geomlds, Matrix3d.Identity)