Following Roy's suggestion in another thread, I went to http://xcell05.free.fr/ and downloaded MoreFunc.xll. Here's what's cool: It has a six functions that handle regular expressions. Instead of complex formulas to extract the filename from
You can use
=REGEX.MID( A1, CELL("filename"), "[^\\]+\.xl[st]", 1, FALSE ) (find one or more characters not including "\" or "[" ending in ".xls" or ".xlt")
I can't comment on speed, because I just got it -- in PERL and some other languages I know it can be very slow.