How to customize an option to a dynamic value (computed by lisp form)

[Jorge]

Hi.  I set three options to a dynamic value, using the value of the option
`org-directory'.  Now my custom-set-variables call in init.el includes the
following:

   '(org-agenda-files
     (list
      (concat org-directory "/agenda/")
      "~/Dropbox/wanessa_e_jorge/administração_clínica/derma-prime.org"))
   [...]
   '(org-icalendar-combined-agenda-file (concat org-directory "/org.ics"))
   [...]
   '(org-mobile-inbox-for-pull (concat org-directory "/agenda/from-mobile.org"))

The problem is that when I try to customize one of these three options, the
customize buffer does not know that the value was computed dynamically.  For
example, the customize buffer for org-mobile-inbox-for-pull shows the value as
simply "~/org/agenda/from-mobile.org".  This means that if I edit the value to
"~/org/agenda/from-mobile42.org" and save the customization, it will be written
to init.el as a string literal, no longer respecting org-directory.  Then if I
later change org-directory I will have problems.

Previously I worked around this problem by setting these options manually
(editing org-init.el, which is called by init.el), but I think the ideal would
be to use customize, so I decided to ask here.  I have already searched Google
and the list archives.

Thank you for your attention.
-- 
• I am Brazilian.  I hope my English is correct and I welcome corrections.
• Please adopt free formats like PDF, ODF, Org, LaTeX, Opus, WebM and 7z.
• Free (as in free speech) software for Android: https://f-droid.org/