repost: how do I launch the program post-install

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SetupCompleteSuccess has the property LAUNCHPROGRAM
and associated properties PROGRAMFILETOLAUNCHATEND and SHOWLAUNCHPROGRAM.

I've tried setting LAUNCHPROGRAM to value 1 when checked. Also value
[PROGRAMFILETOLAUNCHATEND].

But I can't get any exe to launch. Documentation is very unclear. Any clues?

thanks