You will need to use the check box form field in the Legacy Forms toolbox,
which is on the Developer tab (Controls group, Legacy Tools button). If you
do not already have the Developer tab displayed (it is not by default), go
to Office Button | Word Options | Popular and check the box for "Display the
Developer tab in the Ribbon."
From there you'll want to read
http://word.mvps.org/FAQs/Customization/FillinTheBlanks.htm and especially
the forms tutorials by Dian Chapman that this article links to. Note in
particular that, in order to use check box form fields, you must protect the
document for forms, which may not be what you want, but there is no check
box among the new "content controls."
--
Suzanne S. Barnhill
Microsoft MVP (Word)
Words into Type
Fairhope, Alabama USA
http://word.mvps.org