Powerpoint SlideShowBegin won't fire

I have the following VBA code attached in a PowerPoint 2010 macro-enabled presentation:


Public CurrentSlideIndex As Integer

Sub OnSlideShowPageChange()
CurrentSlideIndex = ActivePresentation.SlideShowWindow.View.CurrentShowPosition
If CurrentSlideIndex = 1 Then
MsgBox "First Page"
' some initialization
End If
End Sub


I want to do some initialization there when the first page is shown. The problem is that when I run the presentation for the first time, the routine is not fired. I need to stop presentation and run it the second time, then it work - and keeps working afterward also. Only the first run doesn't work.

I've tried adding something like following in a class module:

Public WithEvents App As Application
Private Sub App_SlideShowBegin(ByVal Wn As SlideShowWindow)
MsgBox "SlideShowBegin"
End Sub


But that doesn't seem to run either.

Pom