Thanks Mike. It's been a while since I worked with scripting and didn't think about that approach. Not being able to test has made this incredibly more difficult. Trial and error is a great learning technique. Someone else will be onsite Friday and can test various permutations for me. We'll just have to see what works for them.

For the time being, I've uncoupled the update and the execution. The app will check for a new version and notify the user, allowing him/her to quit or continue. The user will then run a separate process to do the update. It's not what I want but it's all I can do under the present circumstances.