There is the LAD (last action date) and LAT (last action taken). You should be able to look at those fields. Have a look at the repository reference (just recently posted online) in this topic:
OBJ_M_ACTOR (The “user” table)
http://www.forumtopics.com/busobj/repository5/rpoactor.htm
Dave Rathbun 
(BOB member since 2002-06-06)