players race locked and user/computer

With triggers, how can I detect if a particular peon is building something or not ? I have a trigger setup so that every 5 seconds I issue all of my peons to build something in a region I have setup, this works great, except during the process of building, they stop of course because every 5 seconds they are issued an order to build, so they stop what they were building and start another building... All of the buildings are unfinished. So, if I could simply check to see if they were in the process of building, I could then complete the desired result, which is having my peons build stuff automatically and finish.
I have found a begins constructing event, and the finishes constructing event, but not, "I'm currently building" event.
Any clues ?

Is my question not clear, or has no one ever tried todo this ?

What about changing your construct event ?
Replace the every 5 seconds event with unit finished construction.