Visual Basic for Applications enables building user-defined functions (UDFs), automating processes and accessing Windows API and other low-level functionality through dynamic-link libraries (DLLs). It supersedes and expands on the abilities of earlier application-specific macro programming languages such as Word's Word Basic. It can be used to control many aspects of the host application, including manipulating user interface features, such as menus and toolbars, and working with custom user forms or dialog boxes.
As its name suggests, VBA is closely related to VisualBasic and uses the Visual Basic Runtime Library, but it can normally only run code within a host application rather than as a standalone program. It can, however, be used to control one application from another via OLE Automation. For example, it is used to automatically create a MsWord report from MsExcel data, which are automatically collected by Excel from polled observation sensors. VBA has the ability to use (but not create) (Active X/COM) DLLs, and later versions add support for class modules.* http://en.wikipedia.org/wiki/Visual_Basic_for_Applications
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