CustomDocumentProperties inaccessible through Mac VBA for Excel

I have a workaround for my application using CustomXMLParts rather than CustomDocumentProperties. I can probably rework my application using this in a matter of hours. This change is not backwards compatible and old versions of my spreadsheets will not work.

I have not used CustomXMLParts before, so do not know if I am abusing this feature.

thanks,

Daniel

Sub Test()
    setCustomXMLPart ThisWorkbook, "Test", "Fred"
    MsgBox getCustomXMLPartValue(ThisWorkbook, "Test")

    setCustomXMLPart ThisWorkbook, "Test", "Sam"
    MsgBox getCustomXMLPartValue(ThisWorkbook, "Test")

End Sub

Public Function GetCustomXMLPart(bk As Workbook, strPropertyName As String) As CustomXMLPart
    Dim bookParts As CustomXMLParts
    Dim cp As CustomXMLPart

    
    Set bookParts = bk.CustomXMLParts
    Set GetCustomXMLPart = Nothing
    On Error Resume Next
    For Each cp In bookParts
        If cp.DocumentElement.BaseName = strPropertyName Then
            Set GetCustomXMLPart = cp
            Exit Function
        End If
    Next cp

End Function

Public Function getCustomXMLPartValue(bk As Workbook, strPropertyName As String) As Variant
    Dim myPart As CustomXMLPart
    Set myPart = GetCustomXMLPart(bk, strPropertyName)
    If myPart Is Nothing Then Return
    getCustomXMLPartValue = myPart.DocumentElement.Text

End Function

Public Sub setCustomXMLPart(bk As Workbook, strPropertyName As String, value As String)
    Dim myPart As CustomXMLPart
    Dim valStr As String, xmlStr As String
    valStr = CStr(value)
    xmlStr = "<" & strPropertyName & ">" & valStr & "</" & strPropertyName & ">"
    Set myPart = GetCustomXMLPart(bk, strPropertyName)
    If Not (myPart Is Nothing) Then
        myPart.Delete
    End If
    bk.CustomXMLParts.Add (xmlStr)
End Sub