viewing appointments while scheduling event

["Victor A. Stoichita" <victor@svictor.net>]

When scheduling an event with C-c C-s (org-schedule) a calendar pops up.
While navigating that calendar to choose a date, is it possible to view
the events already scheduled in the agenda for that date?

I found this answer to a similar question: https://emacs.stackexchange.com/questions/30512/show-tasks-during-orgmode-scheduling

It says that pressing "!" should pop to the diary file. I don’t use
the diary file, all my appointments are in org-mode files.

The answer mentions adding the following line to the diary file:
%%(org-diary :timestamp :sexp)

In my init file I have set:
(setq diary-file "~/calendriers/diary")
(setq calendar-mark-diary-entries-flag t)

And in ~/calendriers/diary I have just the following line:
%%(org-diary :timestamp :sexp)

This does work. When trying to schedule an event the calendar is not
opened any more, I just get a message "End of buffer". I suppose that
it’s not the correct way to write the diary file, but I’m unfamiliar
with the diary syntax and could find no documentation for the particular
feature which %%(org-diary :timestamp :sexp) might provide.

Does anyone have a working setup for this?

Regards,
Victor