CST - Export Z touchstone files from VBA Macro interface

Hi,
I am writing a macro to export the touchstone file results from a CST Studio Suite simulation using the Touchstone VBA object. That seems doable for S parameters. However, for Z parameters, I can't get enough information.
Also, how can I control the touchstone file format before the export? i.e. using RI, MA or DB format?
Many thanks in advance,
Mazen