That will work if length is the only other factor involved, but it may not work if the values are the same length with different text or numeric values. From the guy had doesn't have any solution, of course.
I should be upgrading to XP too. The only thing is, that will happen when they release XP2010.
It should work if they all start with "c" and then are followed by the number. If there are other conditions/possibilites, they need to identify them, and then we can modify/create the solution from there.