Build package with subpackages

[Sanjaya Ratnaweera]

Hi all,
   
     I'm new with autoconf tools and I have following problem. I have a
package which contain subpackages. I need to build sub packages before
the main package.

eg.

My Package
          |--- configure.ac
          |--- Makefile.am
          |--- src/
          |--------------pkgA
                               |--- configure.ac
                               |--- Makefile.am
                               |--- src/
          |--------------pkgB
                               |--- configure.ac
                               |--- Makefile.am
                               |--- src/
          |--------------pkgC
                               |--- configure.ac
                               |--- Makefile.am
                               |--- src/

First I need to build pkgA and the built libraries used by pkgB and so
on. All I need to do is build all packages running ./configure in root
directory, but pkgA, pkgB and pkgC want to build before root directory.
Is it possible to do this, if so please give me a hint.

Thanks

    ~sanjaya