[V8i VBA] Convert normal cell to annotation

I created this macro to add annotation scale to selected cells but it seems to work only for "Annotation cells". How to convert also normal cells to annotation cells on-the-fly?

Public Sub getSelectionSet()
   Dim oElEnum As ElementEnumerator
   Dim oEl As Element
   Dim propHand As PropertyHandler
   
   Set oElEnum = ActiveModelReference.GetSelectedElements
   oElEnum.Reset
   While oElEnum.MoveNext
      Set oEl = oElEnum.Current
      
Set propHand = CreatePropertyHandler(oEl)
propHand.SelectByAccessString "AnnotationPurpose"
If propHand.GetValue = True Then
propHand.SelectByAccessString "IsAnnotation"
propHand.SetValue True

      oEl.Redraw msdDrawingModeNormal
      oEl.Rewrite
      End If
   Wend
End Sub