Grouping and Subtotaling by List of People

Hello

I need some help with creating a report. I have an excel form with a list of clients and the sessions they have signed up for. There are two types of sessions per week over a 7 week basis. If a person has signed up for multiple sessions they show up multiple times. I've used the subtotal option and it's almost working. The problem is it groups by 1 option only. I have some people with the same last name so when I subtotal it, I'm 6 people short since a couple people with the same last name but different first name are being grouped as one person. Can I place two criteria for the subtotalling?