Report 121- Customer Balance to date

Groupfooters and footer in this report are not correct! Invoices only can be added when the are ‘open’ in customerentrytable. When for instance the report has datefilter …31-12-99 and the invoice from 12-12-99 is paid in 2000 it shows the closed invoice on the report (= CORRECT) WITHOUT CALCULATING IT IN GROUPFOOTER AND FOOTER ? ARE THERE ANY ALTERNATIVES ?