1.'Push the Freakin Button' may solve your "read only" popup  issue.
Hard to say  without seeing it.

Older versions were freeware. Now shareware.
www.aplusfreeware.com/categories/util/system2.html

2. Could you use a CheckBox that your procedure  checks? : If it's
checked, shut down, else leave excel  running. Or vice versa. I might
use OnTime to ring a warning, say thirty seconds  preceding the shut
down (so that you could have the opportunity to change your mind).