[CentOS] Downgrade an rpm

>Kai, correct me if I'm wrong, but one is allowed to use other programs
>not supplied by CentOS. And surely if the user feels that xyz-1.2.3.rpm
>is giving him problems, and he wants to use xyz-1.2.0.rpm instead that's
>his choice?
>

Well, I have rpmforge enabled for example, and I installed an application from their repo which installed a few dependencies from their repo as well. One of those dependencies was an rpm whose version was higher than the software dev's recommended version.

In that scenario, how does one force a downgrade?

Thanks!
jlc