Time reporting for project managers

I'm wondering how I keep our "traditional" project managers happy with this tool. For example if I plan a sprint with 160 hours of work, and we all update daily to show our burn down, my project manager would like to know how much time we spent per week on the project and how much is left, I had some ideas but seems a bit labor intensive

1) Once the sprint backlog is "approved" by the team, CSV export so the pm can get all the estimated hours
2) Each week export to a CSV so the pm can compare the the approved backlog and see how many hours are left

The issue Im having is for a task, says its 8 hours and the developer spends 12 so he ups the amount in the task during the sprint, but once completed he sets it to zero to show its complete, the pm has no record that it took 12 hours unless he tracks his projects in another tool (like a time reporting tool).

any thoughts ? I had used a tool in the past ( I think scumworks) that showed the deltas on the hours for tasks so it showed everytime the hours where changed for a task and who by so you'd see something like

12 hrs - estimated

actually spent

8 hrs 9/1
5 hrs 9/3
1 hrs 9/3

total 14

any thoughts on how to "manage" this ?