Is there an Outlook event that occurs when a user attaches a document to an email?

Question

I'm working on project to check email attachment size and it notifies the sender when they are trying to attach a large document. I started by using example code shown at http://msdn.microsoft.com/en-us/library/office/aa209975(v=office.11).aspx and it works great as described when running the sub TestAttachAdd(). However, with the code running, when I manually create a new email and attach a file to it, the AttachmentAdd event is not triggered.

Am I using the private sub "newItem_AttachmentAdd" incorrectly for what I'm trying to do?

Or is there another Outlook event that I can use to detect when a user attaches a document (either using the "attach file" ribbon button or by drag-and-drop) to a new email?

Public WithEvents newItem As Outlook.MailItem

Private Sub newItem_AttachmentAdd(ByVal newAttachment As Attachment)
    If newAttachment.Type = olByValue Then
        newItem.Save
        If newItem.Size > 500 Then '500 bytes used for testing purposes only 
            MsgBox "Warning: Item size is now " & newItem.Size & " bytes."
        End If
    End If
End Sub

Public Sub TestAttachAdd()
    Dim olApp As New Outlook.Application
    Dim atts As Outlook.Attachments
    Dim newAttachment As Outlook.Attachment

    Set newItem = olApp.CreateItem(olMailItem)  
    newItem.Subject = "Test attachment"
    Set atts = newItem.Attachments
    Set newAttachment = atts.Add("C:\Test.txt", olByValue)
End Sub

-------------------------- updated with most current working version 1/27/2014

Public WithEvents goInspectors As outlook.Inspectors
Public WithEvents newItem As outlook.MailItem

Private Sub Initialize_Handlers()
    Set goInspectors = outlook.Application.Inspectors
End Sub

Private Sub Application_Startup()
    Initialize_Handlers
End Sub

Private Sub goInspectors_NewInspector(ByVal Inspector As Inspector)
    If Inspector.CurrentItem.Class = olMail Then
        Set newItem = Inspector.CurrentItem
    End If
End Sub

Private Sub newItem_AttachmentAdd(ByVal newAttachment As Attachment)
    If newAttachment.Type = olByValue Then
        newItem.Save
        If newItem.Size > 500 Then '500 bytes used for testing purposes only
            MsgBox "Warning: Item size is now " & newItem.Size & " bytes."
        End If
    End If
End Sub

Answer 1

You need to attach your event handler to the right MailItem object.

Trap the Application.Inspectors.NewInspector event, then retrieve the new item from Inspector.CurrentItem.