How can I integrate with a Windows application which lacks a plug-in architecture?
See the question and my original answer on StackOverflowIf you need to react when a text is clicked, you could try to use the Microsoft UI Automation technology, and in this case, UI Automation Events.
Note that depending on how the application is written, it may or may not work.
You can try the cool Inspect and Accessible Event Watcher tools at least to check if its seems feasible.