Please check the following documentation about RTMT in the CUCM version that you are running on:
http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/service/9_1_1/rtmt/CUCM_BK_C54E214A_00_cisco-unified-rtmt-administration-91/CUCM_BK_C54E214A_00_cisco-unified-rtmt-administration-91_chapter_011.html
On the link above you will be able to see the system and call manager alerts. I am afraid that what you are asking is something that unfortunately is not possible. I give you the fact that you can create custom alerts however, I have only been able to create custom alerts for Performance Counters. Refer to "Performance counters and alerts" section for further reference.