In TFS 2008, I'd like to be able to create a pivot table/chart to show the difference in a specific field between two given points in time. The reason is we put our initial estimates in at the beginning and then update it to the total number of hours we did against the item when we finish. An obvious answer to this, would be two separate fields, one for initial and one for final, but that isn't how it was set up, so the only way I can pull the data is querying against the history of the work item.
I am up for writing a custom SQL query or updating the cube with a new perspective if necessary, but ideally, I'd like to just pull it together with the TFS cube into excel 2007. I was looking at the Work Item History perspective, but I'm just not seeing anything close enough in there.
The Work Item history in the TFS cube indeed exposes the state of the work item fields over time. You can just select the start and end point in the pivot table connected to the cube datasource as the row or column. On the other axis, select the field you want to display. The values in the table will show the values for the fields in both points in time.