AlertHook

When the on alertHook handler is called, it should return a value:

 Return Value  Projector Mode Results                 Authoring Mode Results
 -1            shows a stop/continue dialog box       halts the movie (no dialog box)
  0  default   shows a stop/continue dialog box       presents an error message, halts the movie
  1            continues the movie, no dialogs        brings up the script or debug window
  2            quits                                  brings up the script or debug window