gistfile1.el

(lexical-let 
    ((curbuf 0) 
     (buflist '("shell1"
		"shell2"
		"shell3"
		"shell4"
		"shell5"
		"shell7"
		"shell8"
		"shell9"
		"shell10"
		"shell11"
		"shell12"
		"shell13"
		"shell14")))
  (defun gbj-next-buffer ()
    (interactive)
    (setq curbuf (+ 1 curbuf))
    (if (>= curbuf (length buflist))
	(setq curbuf 0))
    (switch-to-buffer (nth curbuf buflist))))