Automatic matching of 'on-account' customer transactions where customer has zero balance but unmatch

I am wondering if anyone can help me on this one. I am looking for a concurrent process that automatically, once run, checks customer account balances and if the customer balance is zero but has out standing transactions, i.e. an invoice for 500, receipt for 400 and credit memo for 100, then matches these values together to clear the customer account. does this process already exist? Unfortunately the current solution we are designing is using Oracle AR as a non user accessed system so all the data comes in via interfaces so we need a housekeeping process to clear up the customer accounts.