A macro would do it. I don't know Word macros at all but you're looking at something like (Date + 7) in the macro.
Not offering to teach Macros, (I couldn't anyway), but have a look at the article below for an idea;
Also, I see there is a shortcut to add the current date to a doc. May be you can modify that in some way?
I am creating a form and am using Word 2007 to make it. I have used the developer tab and created a calendar field in which the calendar drops down to allow the person inputting to select a date.
Is there a way to automatically calculate/pre-fill a date? Such as 7 days from today?