The invention described herein includes a system, method, and computer program product for adding functionality to an application program. The invention includes a tool which can be used in conjunction with any of a plurality of application programs. The tool can be represented to a user by a tool icon on a desktop. After creating or opening a file or other object with an application program, the user can drag and drop a tool icon representing the tool into the application window. This allows the tool program to operate on the object. A windowing system event handler receives information from a user interface regarding the dragging and dropping of the tool icon. The fact that the tool icon has been dragged and dropped into the application window is reported by the windowing system event handler to a base module. The base module mediates communication between the tool program and the application program. This allows the tool program to operate on the object, which may have been previously locked by the application program. Once the object has been unlocked, the tool can then operate on the object.