So...? Does it still not work?
By the way, you don't have to use strlen. If you're not going to use 'letter' for anything, you may write for(;*s != 0; s++){ ... }.
So... Did it work for you? We are trying to help but most of us will NOT compile some random code we find on this site so you'll have to tell us if this did the trick. Also you haven't stated a goal yet so I'm not sure that we're even headed in the right direction with this code.