There was a question in the AutoCAD Architecture discussion group.
“How can i get dwgname of open drawing in this drawing in property set per vbscript code?”
Here is how it can be done. I use ACA 2009 but it should work with older versions too.
On Error Resume Next
Set app = GetObject(, "AutoCAD.Application")
If the full path and name needs to be use just change ActiveDocument.Name to ActiveDocument.FullName.