To see how to do just about everything you might want to do with dates in Word, check out my
Microsoft Word Date Calculation Tutorial, at:
http://windowssecrets.com/forums/sho...ation-Tutorial
or:
http://www.gmayor.com/downloads.htm#Third_party
In particular, look at the item titled
Calculate the # Days Difference Between Two Dates. Do read the document's introductory material.
As for the automatic calculation, Word won't do that without a macro, which is quite simple. Otherwise, you could just use Ctrl-A, F9, to update all fields in the document.