this problem was already solved years ago. Yes you can get to the "other" properties of an object that are "only" exposed to the programming side of the cad engine. You do it by using this in your vbscript:
app.GetInterfaceObject
best post that eplains the possibilites can be found here:
http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=6057466&linkID=9240657
and here
http://usa.autodesk.com/adsk/servlet/ps/dl/item?linkID=9240657&id=7296778&siteID=123112
also note the items in the attachment to the post I made here in 2007
http://forums.autodesk.com/t5/AutoCAD-Architecture/Parent-object-s-Z-coordinate/td-p/1559875/page/2
Here is the psd code to get the endpoint of a pipe in MEP. This is a moot point since the endpoint x,y,z is now exposed in 2011 as a automatic property set. But the same snippet could be applied to any object and extract any property that is available only on the code side.
RESULT="--"
On Error Resume Next
Set app = GetObject(,"AutoCAD.Application.18.1")
Set aec = app.GetInterfaceObject("AecX.AecBaseApplication.6.5")
aec.Init app
Set util = aec.ActiveDocument.Utility
Set pipe = app.ActiveDocument.ObjectIDToObject("[ObjectID]")
pt1 = util.ConvertToVariantArray(pipe.StartPoint)
RESULT = pt1(2) - [ElevationFinishFloor]
also include this in your PSD to be able to alwasy check what version you are using so you can reference the correct one to get the results.
RESULT="--"
On Error Resume Next
Set app = GetObject(,"AutoCAD.Application.18")
RESULT = "Now running " + App.Name + " version " + App.Version
this was discussed a few times in the old autodesk forums but is difficult to find now.
here is some great posts that show what you can do to get all sorts of stuff into a PSD. Just be aware that the version numbers are wrong so you can't cut and paste to 2011 and make it work.
http://blog.jtbworld.com/2007/01/adt-window-style-type-in-psd.html
http://architects-desktop.blogspot.com/2006_01_01_archive.html
http://forums.autodesk.com/t5/AutoCAD-Architecture/Calling-David-W-Koch/m-p/2667386
http://forums.autodesk.com/t5/AutoCAD-Architecture/Array-Values-In-VBA-VBScript/m-p/1692091