Sorting books on disk with custom fields

[Fleckenteufel]

Hi all,
I want to save my books to disk using a customized sorting path. Therefore I created a new field (using create new column) which also appears in the sidebar.

But when I want to set {#myfield}/... Calibre gives me the error message "EXCEPTION: Value: unknown field #myfield" in the template editor.

Did I specified the field at the right place, or do I have to change something? The tooltip in the sidebar also says "The lookup/search name is '#myfield'."

Would be good if somebody could help.

Erik