How do I interrupt and cleanup gracefully?

[T. R. Ponn]

Hello all,

There are a few places in my app where it would be nice if the user 
could use a "command-period" interrupt to gracefully stop my scripts. 
 So, in playing around, I tried this as a starting point in a new button:

on mouseUp
  repeat
    if the interrupt then cleanThisUp else add 1 to msg
  end repeat
end mouseUp

on cleanThisUp
  put "I'm interrupted" into msg
end cleanThisUp

It does, indeed, stop the script, but always with an error...and I never 
see the final message in the msg box.  This is happening in Rev 2.0.3 
IDE on my Mac (OS9.2.2), but must also work in the standalones when 
completed.

What am I missing?

Thanks in advance for any help you can lend!

Best Regards,

Tim Ponn