[Yum] Multiples repositories

[pedro esteban]

hello,

i want that several computers/clients use the same yum server with a
few packets. The clients have to use this packets unconditionally.
This packets are normal packets that all the repositories have, but i
want the clientes use the packets of my repository (i have modified
this packets).

Can i configure the clients for use various repositoris, and the
clients only use my repository for this modifieds packages? (even this
packages are old versions)
Or i have tu put all the packages of a repository in my server?

Thanx