[wix-users] ExecuteFileInUse

[Parkes, Kevin]

I am trying to add support for Files In Use to my MBA and I see my ExecuteFilesInUse gets called twice:
- the first time, event args Files list contains what appears to be the PID of the running app, the Window title and 6 empty strings
- the second time, Files list contains 2 strings: Window title and Window title with " (Process Id: nnnn)" appended.

I've looked at the WiX sources but I can't quite figure out what's going on
  1) why 2 calls?
  2) will there always be 2 calls? Can I reliably "ignore" one and only display an "in use" message in the other?
  3) can I "fix" it so I only get 1 call?
  4) is there an (simple) example anywhere implementing ExecuteFilesInUse?
  5) any guidelines for handling Files In Use in an MBA?

Thanks
Kevin Parkes