you ARE paying RHEL a boatload of cash for the EXTENDED -EXTRA support for RHEL4
and you are also paying red hat for the normal support for RHEL5
have you asked red hat ? seeing as you ARE paying them for the support
it is called creating a "local" repo
and it is fully documented in the red hat knowledge base
https://access.redhat.com/search/quick?
--- you will have to log in to red hat site first