Count Unique text based on multiple conditions

I'm not sure this is even possible, but here's what I am trying to do. I want to count the number of unique occurrences based on multiple criteria


Name Title Task Week Hours
Joe Smith Manager Meetings 5/13/05 50.00
Jane Doe Assistant Meetings 5/13/05 10.00
Jane Doe Assistant Administration 5/13/05 30.00
Jenny Dee Assistant Meetings 5/13/05 00.00
Jim Jones Assistant Work Papers 5/13/05 20.00

What I want to do here is return the unique count of "Assistants" that booked "Hours" for "Week" 5/13/05. The answer is 2

Any help would be greatly appreciated!
Thanks,
Max