Newb: Different commisions paid based on customer's insurance

I am researching moving our commissions over to NetSuite.  We sell products that are paid for by insurance and based on the type of insurance (and subsequent reimbursement) we pay a different commission.

For example, if a rep sells widget A to Patient B who has Insurance C we pay 100$
If the same rep sells the same widget to Patient D who has insurance E we pay $70

The details of the type of insurance are stored as custom fields in the entity record.  If it were possible to explicitly set a commission amount at the transaction level I would use a script to calculate this based on the insurance type, but from what I'm reading it doesn't seem that you can set the exact commission amount for each SO.