Thanks very much for the reply! At the moment, the problem I'd first like to solve is the second one you described . . . at least if I'm reading you correctly. I want pairs of words that are exactly the same except where one has an R, the other has an S. But I'm very much a newbie and am having a tough time parsing your example code so I cannot tell how it is working . . . would it be possible to walk me through it a bit? In general, are we starting with the first word in the list and testing it against the words below it for the R/S difference and reporting it if one is found, then moving to the next item on the list and testing it against all the ones below it, and so on? Again, many thanks!