Holy cow, I wrote a book!
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.
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.