[plt-scheme] getting the current module directory

I need to get a module's directory from inside the module.  Here's
what I came up with:

(module foo mzscheme
  (define *dir*
    (let-syntax ((current-module-directory
		  (lambda (stx)
		    (datum->syntax-object
		     stx (current-load-relative-directory)))))
      (current-module-directory)))
  (provide *dir*))

This seems to do the trick:

Welcome to MzScheme version 202.6, Copyright (c) 1995-2002 PLT
> (current-directory)
"/home/dougo/fred/scratch"
> (require "subdir/foo.scm")
> *dir*
"/home/dougo/fred/scratch/subdir/"

What I'm wondering is, is this a clever hack or a gross misuse of macros?
Is there a better way to do it?

--dougo at ccs.neu.edu