I have a list like this

A B
Var1 Item1
Var2 Item1
Var3 Item2
Var1 Item2
Var3 Item1
Var1 Item1

I would like to count the number of items in Column . Each item can be counted more than once, but only if the name in column a is different. In this case the resultat should be 5 as the last row has same name and Item number as a previous row and is already counted.

Jan