Sale Commission for Doctor in OpenERP and Bahmni

I am trying to sell a service which needs to reflect in both income and expense account. For example

Sellable Service Name : Consultation Fee for Dr. Joe Income Account : 007 Income from Dr. Joe Price : USD 100

Currently I added below service and set it as the only material of the sellable service above.

Service Name : Fee Payable to Dr. Joe Expense Account : 008 Payable to Dr. Joe Cost Price : USD 30

Scenario (Expected)

Once the sellable service sold, I’d like to have USD 100 in the income account and USD 30 in the expense account. Basically the 30% from the income must go to the doctor.

Can someone shed some light on how to achieve the above in OpenERP 7 ? Or do I have to sell both services as different products ?