Can I find which SO line and revenue commitment line is related to?

We have a need to calculate a special value (CMRR) for our sales orders that can be used to drive commission schedules. Obviously  "Alt. Sales" is ideal for this. CMRR is based on the delta between the start and end dates of the revenue recognition per line (among other things)

We use revenue commitments for all orders.
The revenue start and end dates are only put on the commitment (not the sales order).
The sales order requires the ASA values to be filled in.

PROBLEM:
My script can locate the revenue commitment, and calculate values per line, however, there does not seem to be any accessible link between the lines on a revenue commitment and their originating lines on a sales order. That is to say-- some sales order lines have zero quantity etc, so a revenue commitment with 8 lines may belong to a sales order with 12 lines.