[plt-scheme] How to let a new symbol (created in _syntax-case_) visible at top level ?

#lang scheme
(define-syntax defsymbol
  (λ (stx)
    (syntax-case stx ()
      [(_ name val)
       (with-syntax 
           ([new-name 
             (string->symbol 
              (string-append "nv-" (symbol->string (syntax->datum #'name))))]) 
         (datum->syntax 
          #f
          (list #'define (syntax->datum #'new-name) #'val)
          #f))])))

(defsymbol biz 4)

nv-biz
==> 
expand: unbound identifier in module in: nv-biz

I am pretty sure that I am not the first to ask the question but I can't find the answer. 


André Mayers, Ph.D., M. Ps.
professeur agrégé
Département d'informatique
Université de Sherbrooke
Sherbrooke (Québec) Canada J1K 2R1
tél: +1 819-821-8000 poste 62041
fax: +1 819-821-8200
andre.mayers at usherbrooke.ca
http://www.dmi.usherb.ca/~amayers