"Bernard Liengme" wrote...
From a previous post by JE McGimpsey:

US Government sites are prohibited by law from displaying flashing text
(between 2 and 55 Hz) due to triggering seizures in those with
photosensitive epilepsy.

http://www.section508.gov/IRSCourse/mod02/021401--.html

Many other organizations try to conform to section 508.
....

If one's going for annoying, why not use a Calculate event handler to call a
macro that uses Application.Speach.Speak to tell the user s/he screwed up
then have it call itself repeatedly using Application.OnTime?