Disregard, I have things working. Thanks for the direction Phil.
Message boxes block all foreground script execution and property change propagation. Don’t ever trigger them except by that client’s user action. (Or never at all.) Use a popup window if you need such.
I considered creating a popup, but after some testing the message boxes are more desirable. The users aren’t supposed to be hanging out on these windows, so if they get annoyed with a ton of message boxes, well lesson learned. 
Also, the chances of multiple users selecting and/or editing the same thing is quite rare. Probably better chance to win the lottery.