VBA 异常处理失败？

Question

I have created this script to play a wav file when I receive an email. The point is to play the sound only during business hours. If the email is received outside business hours, no sound will play.

Private Declare PtrSafe Function PlaySound Lib "winmm.dll" _
  Alias "PlaySoundA" (ByVal lpszName As String, _
  ByVal hModule As LongPtr, ByVal dwFlags As Long) As Long

Sub PlayWavFile(WavFileName As String, Wait As Boolean)
    If Dir(WavFileName) = "" Then Exit Sub ' no file to play
    If Wait Then ' play sound synchronously
        PlaySound WavFileName, 0, 0
    Else ' play sound asynchronously
        PlaySound WavFileName, 0, 1
    End If
End Sub

Sub PlayASoundDuringBusinessHours(Item As Outlook.MailItem)

  Dim SecondsSinceMidnight
  Dim SecondsPerHour
  Dim NineOclockAm
  Dim NineOclockPm
  Dim TooEarly
  Dim TooLate

  On Error GoTo ErrHandler:
  SecondsSinceMidnight = Timer
  SecondsPerHour = 60 * 60
  NineOclockAm = SecondsPerHour * 9
  NineOclockPm = SecondsPerHour * 21
  TooEarly = Timer < NineOclockAm
  TooLate = Timer > NineOclockPm

  If Not (TooEarly) And Not (TooLate) Then
    PlayWavFile "c:\windows\media\blahblahblah.wav", False
  End If

ExitProcedure:
  Exit Sub
ErrHandler:
    MsgBox Err.Description, _
    vbExclamation + vbOKCancel, _
    "Error: " & CStr(Err.Number)
    Resume ExitProcedure:
End Sub

I have a rule in Outlook that uses this script when mail comes in and it works! For a while, anyway.

I do not know what the problem is, but once in a while an error occurs in this script and I get a dialog from Outlook that says "Rules in error" and "The operation failed." When this happens, the Outlook rule that uses this script becomes disabled.

Is my exception handling inadequate? What could be causing this error and how do I handle it properly?

Update:

The rule is very basic. It does little beyond executing the script:

Apply this rule after the message arrives
on this computer only
run Project.PlayASoundDuringBusinessHours

Answer 1

Not a direct response to the question but my solution was to switch to ItemAdd.

Examples:

http://msdn.microsoft.com/en-us/library/office/aa171270(v=office.11).aspx http://www.outlookcode.com/article.aspx?id=62