AutoCAD-based products can be used as an Automation controller for other applications
such as Microsoft Word or Excel.

VBA sends messages using the AutoCAD ActiveX Automation Interface. AutoCAD VBA permits
the Visual Basic environment to run simultaneously with AutoCAD and provides programmatic
control of AutoCAD through the ActiveX Automation Interface. This linking of AutoCAD,
ActiveX Automation, and VBA provides an extremely powerful interface. It not only
controls AutoCAD objects, it also can send data to or retrieve data from other applications.

Before you can edit or run a macro from a VBA project, it must be loaded into AutoCAD
first. VBA projects are stored in separate files with the .dvb extension, and are composed of code and class modules, and forms. Since VBA projects
are stored in a separate file, a VBA project can open and close different AutoCAD
drawings during a session which cannot be done with AutoLISP.

Fundamental elements of AutoCAD VBA

Three fundamental elements define VBA programming in AutoCAD.

• AutoCAD – Offers a rich set of objects that include AutoCAD entities, data, and commands.
  AutoCAD programmability is highly desirable. However, you will find that the VBA object-based
  approach is quite different from that of AutoLISP.
• AutoCAD ActiveX Automation Interface – Establishes messages (communication) with AutoCAD objects. Programming in VBA requires
  a fundamental understanding of ActiveX Automation.
• VBA – Provides its own set of objects, keywords, and constants that provide program flow,
  control, debugging, and execution. The Microsoft extensive Help system for VBA is
  included with AutoCAD VBA.

Advantages of using VBA

The AutoCAD ActiveX/VBA interface provides several advantages over other AutoCAD API
environments:

• Speed. Running in-process with VBA, ActiveX applications are faster than AutoLISP applications.
• Ease of use. The programming language and development environment are easy-to-use and integrated
  with AutoCAD after it has been installed.
• Windows interoperability. ActiveX and VBA are designed to be used with other Windows applications and provide
  an excellent path for communication of information across applications.
• Rapid prototyping. The rapid interface development of VBA provides the perfect environment for prototyping
  applications, even if those applications will eventually be developed in another language.

• Programmer base. Programmers commonly know Visual Basic .NET (VB.NET). VBA is similar to VB.NET, and
  opens up AutoCAD customization and application development to these programmers as
  well as those who are willing to learn a programming language beyond AutoLISP.