I use index entries extensively for our product catalog approaching 30,000 entries across 50 individual book sections. However our index entries are based on product features, manufacture, etc. so creating indexes based on occurrences of specific words is not practical for us at all.
This said I cant specifically say I know of a script to find & auto create index entries the way you want. However you can try this URL for applescripts that might work for you.
Hope this helps & best of luck with it.
http://bbs.applescript.net/search.ph...earch=Su bmit
Len