I am trying to figure out how to configure odoo to allow me to record an order line in a sales transaction to Marketing Expenses. 

There are times when we give our customers samples/stock for free. We would like to be able to control this via the the Sales Order, as the free stock is generally a part of the transaction. 

Is there anyway in which I could configure the journal entries for these transactions, where the cost of the product would be recorded to Marketing Expenses instead of Cost of Sales. 

Thanks.