(1) can I interactively call an e lisp function like "org-set-property" and
provide a single argument to it even if it expects 2, e.g.:
(call-interactively 'org-set-protertyt (vector "GRADE" ))? (I don't seem to
be able to pass ANY arguments via call-interactively so maybe I
misunderstand something fundamental).

(2) Is it possible to set the default value for interactive file selection
to something OTHER than the currect directory of the current buffer?
Something like:

(let
  ((base-dir "./Assignment1/"))
  (org-attach--attach))

I'd like to set different base directories when attaching files to subtrees
of different first-level trees in a buffer. I guess I would set the value
for the base directory with a property.

thanks!
Matt