Its not that straight forward - believe me...
So before OLC all costs are posted to the order header. However some posting can be referenced back to the operation e.g. labour, materials, PRs, etc.
But this is where it gets tricky..
The planned costs for labour are not recorded as individual records in CO - instead they are aggregated for the whole order. So you need to programatically determine these operation costs using the same date/costing information that the order used (remember that this may be years in the past).
Materials and PRs pretty easy at operation level, but POs can have different values to the PR...
Then there's the issue of cost postings to the header e.g. unplanned material goods issues and purchase reqs/orders. In addition you may have direct postings to the header e.g. overheads.
It took me a long time to get the report correct. and even then I've had to tailor it to 3 different client's needs because of slightly different CO account configurations.
PeteA