A method of installing a first self-contained data handling application to operate with a second, previously installed, self-contained data handling application having at least one call routine which is executed when the second data handling application is operated, is described. The method comprises a) determining the presence of the second data handling application and, if it is present, b) generating a link to a software routine provided by, and utilizing when executed, the first data handling application, which will be executed by the call routine in the second data handling application.