(setq b (nth I S2))
(setq y (- y0 (* I val)))
(setq z (nth 3 (assoc '10 b)))
(setq xyz_new (list '10 x0 y z))
(setq b (subst (cons '72 0) (assoc '72 b) b))
(setq b (subst (cons '73 0) (assoc '73 b) b))
(setq b (subst xyz_new (assoc '10 b) b ) )
(entmod b)