Sort If Function List Results

To be honest, this is something that I, personally, would use a pivot table for.  If you have your data in a table, and then create a pivot table off it, using Grad Year, and Enrollment Date for the rows, and Count of Name for the values.  If you have some that have blank email addresses, you can set email as a filter, and not display the blanks.  On the attached mock-up, you can see all of the information on the Data tab, but then, on the Pivot tab, you can see the pivot table.  The first level of the rows column is the Grad Year.  If you expand that, it lets you drill down on the year for the Enrollment Date, and then the Quarter, then the Month.  Once you get to the level you want, you can double click on the number in the Count column, and it will create a new sheet with only the data that fits your criteria.