stopping shutdown on Mac OS 9

[Brad Allen]

I'm building a Rev standalone for Mac OS 9 PPC which I'd like to put 
in the Shutdown Items of Mac OS 9 and have it run before the computer 
shuts down. What happens, however, is that my standalone gets 
launched and then immediately quits as the OS tries to shut down all 
running apps.

How can I get my standalone to protest the shutdown, as do other apps 
that happen to have open unsaved documents? (I tried throwing up a 
modal dialog, but that didn't stop the shutdown.)

Thanks...