YUM: How to prevent EPEL from upgrading packages installed from other repos?

I would love to leave EPEL made it possible for and also configure it to permit upgrading just the plans that were mounted from EPEL itself to begin with (plans which were by hand mounted from EPEL as a result of details demands). Exists a yum conf instruction to permit this?

• CentOS 6.4
• Yum 3.2.29