Try something like this:
(defun c:foo (/ e elev ss)
(if
(and (setq elev (getdist "\nEnter elevation: ")) (setq ss (ssget ":L" '((0 . "MULTILEADER")))))
(while (setq e (ssname ss 0))
(entmod (mapcar '(lambda (x)
(if (member (car x) '(10 12 110))
(list (car x) (cadr x) (caddr x) elev)
x
)
)
(entget e '("*"))
)
)
(ssdel e ss)
)
)
(princ)
)