Incrementing pick points alphabetically

I know how to increment pick points numerically (see below). How is it done alphabetically?

(defun C:test (/ pt# pt)
   (setq pt# (getint "\nEnter number: "))
     (while
       (setq pt (getpoint "\nSpecify point: " ))
         (if (/= pt nil)
           (progn
             (command "TEXT" "M" pt "" "" pt#)
             (setq pt# (1+ pt#))
           )
         )
      )
 (princ)
)