See http://www.word.mvps.org/FAQs/MacrosVBA/SpellcheckProtectDoc.htm.

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Jay Freedman
Microsoft Word MVP FAQ: http://word.mvps.org
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> How do you get spell checker to work in a Word form? When I create
> the form spell checker will no longer work within the fields. It
> will work outside of the field if I unlock the sheet and type
> anywhere on the page. I would like my user filling out the form to
> have the advantage of spell check.