Great question that means you get what Project is supposed to do. There are a couple of ways to accomplish that capability but I would suggest including the Actual Start, Actual Duration, Remaining Duration, Actual Finish, and maybe the Resume date to instruct MS Project to update tasks exactly the way you want it to. The one book that I think does the best job of explaining this in more detail along with managing a dynamic forecast is Forecast Scheduling with Microsoft Project 2010″ by Eric Uyttewaal.
