A customer wanted to know how they could monitor and intercept taskbar notification balloons. In particular, they wanted to intercept the clicks on a particular balloon and take alternative action.
There is no supported mechanism for intercepting taskbar notification balloons or redirecting clicks on them.
Imagine if that were possible: Fabrikam would intercept notification balloons for Contoso. If they had access to the balloon text itself, they might change the message from "Contoso products are back in stock. Click here to place your order." to "Special offer for Contoso customers: Take 10% off your first order from Fabrikam."
If they could intercept clicks, then Fabrikam might take clicks on the balloon that normally send the user to the Contoso ordering dialog and instead sends them to a Web page where they can download Fabrikam Supply Chain Management Software.
And then Contoso would ask for a way to block the interception because Fabrikam is preventing their software from working. And then Fabrikam would say "Infinity", and then Contoso would say "Infinity plus one."
While those two programs are busy fighting over who gets the clicks, LitWare sneaks in and says, "I want to steal the clicks that those two companies are fighting over, so I can display my custom user interface instead."
The only way to win is not to play the game. There is no facility for intercepting balloon notifications or redirecting their clicks. The application which creates the balloon decides what the balloon says and what happens if the user clicks on it. If you want to alter the text or behavior of a balloon notification, you get to work with the developers of the application that is displaying the balloon and see if they are willing to give you a way to intercept their messages and clicks.