Unlike Microsoft’s development tools, Office has not yet made the move to the .NET Framework and managed code. Although some workarounds allow developers to build managed code for Office, a full solution is not likely until “Office for Longhorn.”

Word and Excel expose their functionality to developers via COM APIs. Developers then build on those APIs using Visual Basic for Applications (VBA)-the built-in programming environment derived from Visual Basic and included in Word and Excel. Even the macro recorder feature included in each product generates VBA code. This environment has proven popular with some IT organizations, allowing them to customize Office to their specific business needs.

But while Office continues to use VBA and COM, Microsoft’s developer products, most notably Visual Studio .NET, have moved to the .NET Framework, giving developers a more robust and easier-to-use programming environment, as well as the choice of multiple programming languages. To help bridge the gap between Office and .NET, Microsoft makes available an add-on to Visual Studio .NET-the Visual Studio Tools for Office-that layers a set of .NET APIs on top of the COM APIs in Office. But unlike VBA, which is built into Office and therefore available to sophisticated end-users who create and edit macros, the Visual Studio Tools for Office require Visual Studio, which is targeted exclusively at developers.