If you want to limit a user to entering data into specific parts of a document with Word 2003 & earlier, you can use formfields and document forms protection. No code required. See:
http://word.mvps.org/faqs/tblsfldsfms/LinesInForms.htm
http://gregmaxey.com/word_tip_pages/repeating_data.html

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]