PeopleSoft Single invoice for fixed fee and rate based contract lines

We have some new contracts having both fixed fee billing from contracts bill plan events and rate based transaction from Project Costing. For sending the transaction to billing, Contracts to billing interface process needs to run one for fixed fee billing and then they have to run as-incurred billing for PC transactions. This results in 2 temporary invoices to billing worksheet. Is there any way to consolidate into single invoice for fixed fee billing and PC transactions so that we can invoice the customer via single invoice?