NPCs that know when they're doing something?

This is basically simple. I have a bot that needs to perform action A, and once completing action A, does action B, and so on. The quick fix for this is 'do A, schedule B,' but that requires knowing how long A will take. I grabed the Task Manager system from AiPlayer in the fps demo, which does a good job keeping track of what tasks to do, but it doens't provide the bot with any idea of when he's completed one task and should move on to another. Any thoughts?