There is no CICS ICE variable to focus on to get this information. However, CA SYSVIEW can monitor and generate an Alert for when the ICE transaction falls off the chain.
From Sysview on the CTHRESH screen, you can set a threshold for TSUMRATE, specifying the CICS region(s) being monitored and a resource name of the ICE transaction (ie:CEMT, CESF, etc..). The Ruletype would be LOWER, and the LIMIT and WARNING should be set to reflect 0. This will allow for an alert to be generated when the transaction falls off the chain.