Have Cost Plus Prime Invoice Populate Sub Invoice at the Less Retainage Amount

Can we add an option for Cost Plus Prime Invoices to populate Sub Invoices at Net Totals (less retainage being held on them)? I have Clients who do not hold Retainage on Prime Invoices for the Clients, but they are holding retainage on Sub Invoices which cannot be invoiced to client before they pay it out. Currently all invoices applied to Cost Plus come through at Gross Totals inclusive of retainage. We are currently doing a work around of holding retainage but they need to go into the release retainage on every invoice to release held retainage on all bills or invoices that are not holding retainage, so it is very tedious.