One could be created but it seems a bit pointless so you would need to convince us as to why it would be useful. The process described below would be far faster to perform manually than it would be to create with a macro. The macro therefore only makes sense if you need to do this on a regular basis.

The basic workflow I would follow would be to:
Copy the entire document as text only into a new blank document
Replace all the spaces with returns to make a series of one word paragraphs
Sort the text alphabetically
Loop through all the paragraphs and remove all empties and duplicates (possibly do this Excel for simplicity)
Save this doc (for use as the concordance file)
Now with the original doc, run the autoindex function with the new doc as the concordance file.

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Andrew Lockton
Chrysalis Design, Melbourne Australia