Return unique User Id's

[Rob Kazan]

I have a sheet in which I need to figure out which sets of values in column B do not have repeating numbers of Column A. For example column A lists Family ID's and Column B lists Grades. How many sets of grades have ALL unique ID's , I.E grades 5 and 6 have all unique Family ID's with no repetitions, as do grades 3,4. Two grades per unique set is all I need . If anyone can help it would be much appreciated. Example attached.