I assume you mean that you want to do something (run a VI) when a user tries to exit the LabVIEW development environment. I do not know of a way to pick that up as an event. You can run a VI that monitors all other running and/or open VIs in LabVIEW and trigger actions when they stop or close.
If you really want to do something other than exit when a user selects exit, build a custom runtime menu and capture the tag assigned to File>>Exit (or quit). You can do anything you want when the user selects that item or any other for that matter.
Daniel L. Press
PrimeTest Corp.
www.primetest.com