Well, if I understand correctly you want to create a projection, right? But you are using the invoice tables to gets COGS (which makes some sense as it it calculated there) but that is after the fact.
What you would need to do is use the live Sales Order data (BKARINV and INVL) and do the calculation within your report. You would probably need to also bring in the BOMS of your top-level sales order items and then the actual cost fields from the items in the those BOMS in order to calculate it and then populate your report.
Sounds like a BIG undertaking to me, especially in Crystal....