Illegal function call in (jurosParaAcrescimo 3.0)

;; FOO

;; globals
(defvar Quantidade 3)
(defvar Composto 1)
(defvar Periodo 30.0)
(defvar Pagamentos '(30.0 60.0 90.0))
(defvar Pesos '(1.0 1.0 1.0))

;; function to sums Pesos()
(defun getPesoTotal()
  (_getPesoTotal(- Quantidade 1))
)

;; recursive function who REALLY sum Pesos()
(defun _getPesoTotal(valor)
  (if (= valor 0)
    (nth 0 Pesos)
    (+ (nth valor Pesos) (_getPesoTotal(- valor 1)))
  )
)

;; this function doesn't works (it's incomplete either)
(defun jurosParaAcrescimo(juros)
  (if (or (or (<= juros 0.0) (<= Quantidade 0)) (<= Periodo 0.0))
    0.0
    (
      (let pesoTotal (getPesoTotal))
      (if (<= pesoTotal 0)
        0.0
        6.0  ;; FAKE, while I don't write the real calculation
      )
    )
  )
)

;; tests
(princ "Peso total = ")
(write (getPesoTotal)) ;; this works
(terpri)
(princ "Acrescimo = ")
(write (jurosParaAcrescimo 3.0)) ;; this doesn't works

; ERROR:
; file: D:/Lisp/juros.lisp
; in: DEFUN JUROSPARAACRESCIMO
;     ((SETQ PESOTOTAL (GETPESOTOTAL))
;      (IF (<= PESOTOTAL 0)
;          0.0
;          6.0))
;
; caught ERROR:
;   illegal function call
;
; compilation unit finished
;   caught 1 ERROR condition