[plt-scheme] Setting current-slide-assembler and margin from module

Hi all,

I'm defining some help functions which abstract my way to build slides
so I don't have to do all over again every time I need to create a
presentation. Problem is I can't seem to set-margin! and
current-slide-assembler from the module where I have the functions.

I have:
(module slide-help mzscheme

(require (lib "slide.ss" "slideshow"))

<help functions>
(set-margin! 0)
(current-slide-assembler ...)

)

and then my presentation:
(module presentation (lib "slideshow.ss" "slideshow)

(require "slide-help.ss")

<slideshow>

)

Still, I get that current-slide-assembler is undefined in slide-help
as well as set-margin!.
How can I do this?

Cheers,

-- 
Paulo Jorge Matos - pocm at sat inesc-id pt
Web: http://sat.inesc-id.pt/~pocm
Computer and Software Engineering
INESC-ID - SAT Group