Automation projects created with the AutoCAD 2009 VBA IDE, or earlier, or Visual Basic 6 will have to be recompiled to work with AutoCAD 2011.

AutoCAD 2011 automation projects use the type library acax18enu.tlb. The type library is located in the following folder: C:\Program Files\Common Files\Autodesk Shared.

AutoCAD 2011 automation projects use the AutoCAD.Application.18 ProgID for the CreateObject, GetObject, and GetInterfaceObject methods. For example, if you are using the CreateObject function in an AutoCAD 2011 automation project, you use CreateObject ("AutoCAD.Application.18"). If an automation project uses version-independent ProgIDs, change the project to use version-dependent ProgIDs.