Implementing an interface in ThisOutlookSession is not working in Office 2013 - vba

Question

I have an Outlook macro I wrote that will automatically mark items as read when I move them to a folder. (I hate having unread messages in folders other than my Inbox.) I wrote the macro in Outlook 2010, and it's been functioning well for years.
I recently upgraded to Office 2013, and now my macro doesn't work--I'm getting a type mismatch error on this line (see below for the full code):
Set oMoveHandler.Callback = Me
oMoveHandler.Callback expects an object of type IMessageMoved, which the object implements, so I'm not sure why I'm getting this error. Any ideas?
ThisOutlookSession code:
Option Explicit
Implements IMessageMoved
Private m_oFolderCollection As Collection
Private Sub Application_Quit()
Set m_oFolderCollection = Nothing
End Sub
Private Sub Application_Startup()
Dim oFolder As Outlook.Folder
Set m_oFolderCollection = New Collection
For Each oFolder In Application.GetNamespace("MAPI").Folders
Call AddFolder(oFolder)
Next oFolder
End Sub
Private Sub AddFolder(Folder As Outlook.Folder)
Dim oFolder As Outlook.Folder
Dim oMoveHandler As MoveHandler
If Folder Is Nothing Then
Exit Sub
End If
If Folder.Folders.Count = 0 Then
Exit Sub
End If
For Each oFolder In Folder.Folders
If oFolder.DefaultItemType = olMailItem Then
If oFolder.Name <> "Inbox" And oFolder.Name <> "Outbox" And oFolder.Name <> "ePrescribing Workgroup" Then
Set oMoveHandler = New MoveHandler
Set oMoveHandler.Folder = oFolder.Items
Set oMoveHandler.Callback = Me
Call m_oFolderCollection.Add(oMoveHandler)
Set oMoveHandler = Nothing
End If
Call AddFolder(oFolder)
End If
Next oFolder
End Sub
Private Function IMessageMoved_MessageMoved(Item As Object) As Variant
On Error Resume Next
Item.UnRead = False
On Error GoTo 0
End Function
IMessageMoved:
Public Function MessageMoved(Item As Object)
End Function
MoveHandler:
Private WithEvents m_oFolder As Outlook.Items
Private m_oCallback As IMessageMoved
Public Property Set Folder(Folder As Outlook.Items)
Set m_oFolder = Folder
End Property
Public Property Get Folder() As Outlook.Items
Set Folder = m_oFolder
End Property
Public Property Set Callback(Object As IMessageMoved)
Set m_oCallback = Object
End Property
Private Sub Class_Terminate()
Set m_oFolder = Nothing
Set m_oCallback = Nothing
End Sub
Private Sub m_oFolder_ItemAdd(ByVal Item As Object)
If Not m_oCallback Is Nothing Then
Call m_oCallback.MessageMoved(Item)
End If
End Sub

Answer 1

I suspect I was actually running into a similar issue to the one described in this post describing a similar problem in Excel where binding just wasn't working as expected. To work around it, I ended up moving my interface out of ThisOutlookSession into a separate class which I then just instantiate from ThisOutlookSession.