Thanks to several helpful threads here I know how to determine the bitness of an Office app, which I need to do prior to installing my add-in.
However, unlike @Catalin's excellent tutorial and sample installer, I don't have a mixed bitness install. Instead, if the bitness is wrong I want to halt the installation altogether. And I want that to be the very first check.
I've created the appropriate searches to determine bitness and set up a custom launch condition, but I know I can't control the execution sequence of launch conditions.
How do I run the searches, halt the installation, and issue and an appropriate error message if the bitness is wrong?