Include Unbilled PPM invoices in Available Credit Check

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Our client woul like to leverage the Credit Management module, however they are having difficulties with the available credit calculation.  The available credit only takes into account Open AR balances and credit authorizations in OM.  They want to include unbilled invoices in PPM and other modules which integrates to AR.  Can this be accomodated?  Withouth creating an credit check failure or creating a report, is there any other way to check the available credit for customer?