To get the date, you get the Value property of the calendar control. After
the user clicks the date, have a button or other object that the user can
click to indicate that they are done. This gives them a chance to correct
the date if they click the wrong one. When the user clicks the button, hide
the form (.Visible = False) that the calendar is on. If you opened that form
with the acDialog window mode argument in the DoCmd.OpenForm call, the code
will pause until you hide the calendar form. You can now get the value of
the calendar in the next line of that code.
A calendar that works better has been developed by Stephen Lebans. You can
find it at:
http://www.lebans.com/monthcalendar.htm