Voiding out Return Authoizations on Commission Reports

I apologize in advanced. I pretty much have no idea where to being on this, but I am a certain there is a better way to do this.  For commission calculations we don't count things in the return authorization process as gross profit for commissions.  Therefore all transaction associated with the RMA such as item receipt, item fulfillment, credit memo (if any), invoice do not count. Right now we have to manually go through and scrub commission reports, around 2,500 lines.  This consists of going through almost ever line, and then zeroing out amounts (cost, profit, revenue) on the items