From any Windows application that allows, for example, an extension by macro programming and supporting DDE, you can establish a link to the database using QueryPlus. To do so, you must extend the application by programming the DDE link to the database.
You can use the example templates ADABASX.DOT (Microsoft Word 6.0) and ADABASX.XLM (Microsoft Excel 5.0) provided in the directory <DBROOT>\QUERYPL\MACROS\SAMPLES and adapt them to your application or according to your requirements (see Section DDE Support of QueryPlus).