replacing all non [a-z] chars possible?

Hi there, I am wondering if it would be possible to replace all chars which are not inbetween [a-z] with a valid asccii coresponding to it. I have a db with a bunch of citynames and I would like to create valid filenames out of those. The prob is, that I do not know all special chars. For example there was one: ï which I did not know. So maybe there are a lot others similar like that. The point is, how could I create a valid filename out of those citynames which contains only the chars from a - z? I tryed erregrplc, but I do have to know the char for that. Thanx for any help, andy