vb.net - Outlook - Counting the number of items in a conversation

Merry Christmas guys ...

I am implementing a function will will return the number of items in an Outlook Conversation - I have cobbled the following together and whilst no error is thrown - it doesnt seem to return the correct count:

    Function GetConv(mailItem As Outlook.MailItem)
        Dim Conversation As Outlook.Conversation ' Get the conversation
        Dim Items As Outlook.SimpleItems
        Dim expMessage$

        '   // If Item = a MailItem.
        Try
            If TypeOf (mailItem) Is Outlook.MailItem Then
                Conversation = mailItem.GetConversation
                If Not IsNothing(Conversation) Then
                    Items = Conversation.GetChildren(mailItem)
                    GetConv = Items.Count
                End If
            Else
                GetConv = 0
            End If

        Catch ex As SystemException
            expMessage = ex.Message
            MsgBox(expMessage)
            GetConv = 0
        End Try

    End Function

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Can someone assist to ensure that the correct count of the items in the conversation are returned?

MTIA

DWE