Word doesn't really have a feature to lock a single cell the way Excel does.

If you have Word 2003, and if everyone else to whom you'll send the document
also has Word 2003, you can use the new editing restriction feature in the
Protect Document task pane -- select everything except the cell you want to
lock, and check the exception box for Everyone. That will leave just the
unselected cell with protection.

In any earlier version of Word, make a protected form
(http://www.computorcompanion.com/LPMArticle.asp?ID=22) and insert form
fields in the table wherever users should be able to edit. If they should
also be able to edit parts of the document outside the table, insert section
breaks and protect only the section containing the table (Tools Protect
Document for forms Section). But there will be a number of features that
aren't available even in the unprotected sections; see
http://word.mvps.org/FAQs/MacrosVBA/...ProtectDoc.htm for a
workaround.

--
Regards,
Jay Freedman
Microsoft Word MVP FAQ: http://word.mvps.org