Conditional compilation of program

[Jose Roman Bilbao]

Hi, 

I have read on the Automake manual that to conditionally build programs
I need to write all the optional names in EXTRA_PROGRAMS and substitute
from autoconf in bin_PROGRAMS, well, I have written this in
configure.in:

PHAN3D = phan3D
AC_SUBST(PHAN3D)

and this in the conditional program's Makefile.am:

bin_PROGRAMS = @PHAN3D@
EXTRA_PROGRAMS = phan3D

but it does not work, any clue? any problem when building just optional
programs? Should I make conditional directories instead? (My program is
in a separate directory).

Thanks.