If you haven't yet invested much time and energy in using the Calendar
control provided with Access then I recommend that you take a different
route. Ken Getz et alia provide a calendar form and module on the CD
accompanying each edition of "Access [YourVersion] Developer's Handbook"
that you can copy into your applications and tweak to your heart's content.
I believe that there are also examples of calendars on
http://mvps.org/access. The beauty of using calendars from either of the
above sources is that they will then be invulnerable to OS glitches and the
version issues that can arise when upgrading your application to a newer
release of Access.
hth