[plt-scheme] Attaching contracts to unit exports

Hi all,

I'm trying to attach contracts to a unit exports using
define/contract. For an export foo I have in unit body:
(define/contract foo
...
...)

Well, it doesn't work since I cannot export syntax from a unit (Dr's words!).
So, since I cannot also use provide/contract since it is not a module.
Is there any way to attach contracts to units export values?

Regards,

-- 
Paulo Jorge Matos - pocm at soton.ac.uk
http://www.personal.soton.ac.uk/pocm
PhD Student @ ECS
University of Southampton, UK