>>>I want to index on the last three letters of a file name
>>>and get a list indexed by file extension.
>>
>>Assuming that you have filenames loaded into a "files" column of a table:
>>
>>INDEX ON RIGHT(ALLTRIM(files),3) TO ext_index
>---
>Hi John and that works - thanks :))

Or load foxtools and:

INDEX ON JustExt(file) TO ext_index