Non-labor Cost and Percent Complete for "this period"

I have a project with non-labor resource costs assigned. The owner wants to see Earned to Date and Earned this Period.  When I update a previously updated non-labor cost, I have to take it to zero percent complete before I change it or the Earned this Period, Remaining Cost and at Completion Cost miscalculate. When I do this, the "this period" is really the earned to date; therefore, I have no "Earned this Period." It is noteworthy that there are no Earned to Date selections for Cost columns. Any ideas? Am I doing something wrong?

Thanks,

Rob