Howto: Xcode project universal with ppc and x86 assembler ..

How to make a "universal" project with objective C source and ppc and
x86 assembler sources.
Both (.s) assembler source has the same name for subroutine.
I can call assembler subroutine from C without problem using two
project: one for ppc and an other for x86.
I can also do a "universal" project but only with a single assembler
source (ppc or x86 both not both)
I wish merge the ppc and x86 as a "universal" project holding both ppc
and x86 assembler source.
As soon as I try to add a second assembler source to a "univeral"
project Xcode complaint architecture problem...