[CentOS] how to use my rpm to replace default old version rpm in centos?

Hi all,
  I have installed a software using "yum install ...", but the
version of rpm in centos is too old.  I have made a new rpm from
source, and now I'd like to use this to replace the old version rpm in
centos cd. So, When I install centos for my computer, I can choose
to install it automaticly.
 In my guess, I have to replace the rpm at first. After that, I
need to edit something such as dependencies.
 Who can tell me how?
 Thanks a lot.

Best Wishes!
Qiang Ma