Elisp - Elements in tlist is not being updated with the new values

[steve-humphreys@gmx.com]

Am trying to use more let constructs.  The problem is that the elements in tlist
is not being updated with the new values.

(defun timgrid (tstr tend tpd)

   (let* ( (timu tstr) (tfr tstr)
           (tlist (list tstr))
           (frc (/ 60.0 (float tpd)))
           (cnt (* (/ (float (- tend tstr)) 100.0) frc))
           (i 0) (k 0))
      ;; ----- body of let -----
      (message "frc: %f" frc)
      (message "cnt: %f %d" cnt (truncate cnt))
      (message "tlist: %s" tlist)

      (dotimes (i (truncate cnt))
         (let* ( (tfr (typh-timfutur timu tpd))
                 (timu tfr) )
            ;; ----- body of let -----
            (setq k (+ k 1))
            (when (string-equal lgfun "t")
               (message "Iteration: %d %d %d %d" k timu tpd tfr))
            (setq tlist (append tlist (list tfr))) ))
      (message "%s" "* timgrid")
      (message "tlist: %s" tlist)
      tlist ))