[MS CE up15] Trying to store a configuration variable in the attachement filename

I have tried this to be able to make my reference files portable

https://docs.bentley.com/LiveContent/web/MicroStation%20Help-v19/en/GUID-6CD8765F-908C-68F9-5352-73435874C285.html

But the variable seems to be resolved and not stored in the attachement filename

Am i missing something ?

Many thanks