Charging a discount to marketing budget

Hi, my nonprofit offers astronomy courses, between 6 and 12 per year.  We sometimes (but not always) offer a discount off the price for a course for someone who has never taken a course with us before.  So for example, if a course is priced at $600 and we give a $100 "1st timer" discount, we will have a mix of students who paid either $500 or $600 as the case may be.  I understand how to set up and use discounts on sales receipts in QB Advanced.  But the issue is:  we consider this discount a form of marketing for our courses in general, and I would therefore like to charge it to our marketing budget.  Is this possible in QB without double-counting it or do I have to do it outside of QB on a spreadsheet?

Thanks for any suggestions!