Abstract: An add-on application, running on a computer, allows a user to store, in a repository, information such as (for example) document images, and to associate particular information with specified states of a host application such as the QUICKBOOKS® accounting software. When the add-on application determines, for example, that a bill is being displayed (or is about to be displayed) on the screen by the host application, the add-on application automatically obtains, and displays on the screen, information associated with the bill, such as a list or count of one or more electronic documents that are associated with the bill. In our particular embodiment, the auxiliary window is a toolbar or sidebar window located within the host application window itself. The foregoing is achieved utilizing standard host-application SDK and operating-platform API functionality, thus reducing the risk of degrading the host application's performance.