Use a macro button field. See the article "Using MacroButton fields†at:
http://www.word.mvps.org/FAQs/TblsFldsFms/UsingMacroButton.htm
The macro that is run by the button can either insert a specific file of
display the Insert Picture dialog for the user to select the file that they
want to insert. It will probably be necessary to include in the macro code
to Unprotect and Reprotect the document.
--
Hope this helps.
Please reply to the newsgroup unless you wish to avail yourself of my
services on a paid consulting basis.
Doug Robbins - Word MVP, originally posted via msnews.microsoft.com