Work Data Sheet is not a structure of Project, are you talking about the Work Breakdown Structure? (WBS) as far as "getting the information into it" I am assuming you have a separate template or document with the data from the completed job to look over. Manually enter the changes, there is no easier way! If I am incorrect please clarify!
Ah, so you need one of these!
See the link above for the lesson on tracking in MS Project, should get you where you need to go! :)
File>>Options>Schedule-Calculation check to see that "calculate project after each edit" is checked