How to get all dependent source packages

[sha liu <sandyleo26@gmail.com>]

Hi everyone,
   What I want to do is:
   If I want to build a package(for example dpkg) from source, how
should I recursively get all the dependent *source* packages of it?
This means not only the direct dependency of the package but also the
dependent of the dependent...I know "apt-get build-dep" will only
*install* the dependent *binary* packages.
   I want to do this because I need to build dpkg on a CLFS system
(think it as a minimal linux system without debianization), and it's
crazy to download all dependent source packages of dpkg, right?
--
Best,
Sha Liu