You can use a pivot table to summarize the data. Using your example: In
Excel 2007, Select the data, Select "Pivot Table" on the Insert tab, then add
fields from the Pivot Table field list as follows:

Row Lables = A, B
Sum Values = Count of B

You should get a table that shows each person's name, the grand total of
occurances per person, then a total number of occurances per date per person.

As you add occurances to the data list, you will need to update the pivot
table by clicking the "refresh" button on the Pivot Table Options tab.

Hope that helps!