(defmacro eval-with (syms &body body)
  `(eval `(let (,,@(mapcar (lambda (b) ``(,',b ',,b)) syms))
            ,@',body)))

;; (let ((a 10) (b 20))
;;   (eval-with (a b)
;;     '(+ a b)))

;; ==>

;; (let ((a 10) (b 20))
;;   (eval `(let ((a ,a) (b ,b))
;;            (+ a b))))