This is about the closest I could find, not sure if its specific enough for you:
.1.3.6.1.4.1.9.9.63.1.3.1.1.2
cvCallActiveTxDuration OBJECT-TYPE
-- FROM CISCO-VOICE-DIAL-CONTROL-MIB
-- TEXTUAL CONVENTION AbsoluteCounter32
SYNTAX Gauge
MAX-ACCESS read-only
STATUS Current
DESCRIPTION "Duration of Transmit path open from this peer to the voice gateway for the call leg. This counter object will lock at the maximum value which is approximately twodays.