Filtering multiple portals in same layout
I am creating an invoice for therapy services in FMP11. My Invoices table if linked to my master ledger in such a way so that, for example, September's Invoice for patient A will only pull in service records from patient A's master ledger 1) if the service record's Month(Date of Service) matchs the Month(Invoice Date). I want 1 portal to show sesssions (and their payments) that occurred during September, and a second portal to show records of sessions that occurred during prior months, but the insurance payment arrived in September.
I got the two portals filtered just fine: portal one shows the current months' sessions, charges, etc., and the seocnd portal shows records form prior months that had insurance payments come in during the current month.
The problem is getting the Current Charges calculation field to tally only the charges for the new sessions that are are shown in portal 1. Just like the FMP11 manual said it would, this calc field is summing all of the related records, including those in the second portal. So, for patient A who had 3 sessions in current month @$100/sesssion, and also had insurance payments come in during the current month for 3 sessions than had occurred during a prior month (which had also been billed @$100/session), the Current Charges calculation field - Sum (Master Ledger::Charge ) - tallys $600 instead of $300.
Am I trying to do the impossible?