I'm trying to count the unique values given several conditions, for example
in the example below, count the number of unique Item_num's that were sold on
Wed during the Morning, which would return 2:

A B C
1: Item_Num Day Time
2: 1 Wed Morning
3: 1 Wed Morning
4: 2 Thur Evening
5: 2 Thur Evening
6: 3 Thur Morning
7: 3 Thur Morning
8: 4 Wed Evening
9: 4 Fri Evening
10: 5 Wed Morning
11: 5 Wed Morning