I ran into Jorge Lopez while at Autodesk University this year.  What a pleasant surprise as I had not seen him in a few years since he left Autodesk. Jorge is a programming wizard and was the original developer of the AutoCAD Dockable Container. Many people have used this tool in the development of their AutoCAD customization. Jorge has now launched a web site for this tool at www.jrl-e.com .

Description from Jorge's web site:
"This application is a tool for 3^rd party developers who are interested in developing UI applications for AutoCAD 2000-2005 without the need for C++ and ObjectARX. It provides a docking window that serves as a generic and programmable container of ActiveX controls. ActiveX controls can be created with a variety of tools such Visual Basic and Delphi. This enables easy creation of modeless UI applications using the language of your choice. AutoCAD can then be customized from your ActiveX control via the AutoCAD Automation Object Model."