Project Invoice and Revenue Budget Version

I am creating a AIA like invoice that will print from the Oracle Project Billing Module.  One area on the invoice has a detail schedule of values for each of my top task.  I need the ability to print the budgeted revenue (as my schedule of values).  Normally, this is not an issue.  However, we are a heavy highway company and our projects are unit priced.  If our units installed exceed the planned quantity, we just increment the revenue budget.  So, I need the ability to get information of the baselined version that was available at the time of the