How to modify and save a word document into two places at the same time and later to modify them again only to write and modify in one word doc and not write anything in the other? 

Cross-posted at: https://social.msdn.microsoft.com/Forums/office/en-US/94103c70-5dc7-4600-88d5-6d1ed8527ce7/how-to-modify-and-save-a-word-document-into-two-places-at-the-same-time-and-later-to-modify-them?forum=worddev
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See http://www.gmayor.com/SaveInTwoPlacesAddIn.htm.