Hi everyone! I'm hoping someone here can help me with this:

I have a set of data for which Column A and Column B each consist of non-unique 8-digit number values. A single value in Column A can occur multiple times in the data and can have multiple different corresponding Column B values.
I want to create a new column(Column C) that displays the number of unique values in Column B per value in Column A.

For example, if I have:

|____ColumnA____|____ColumnB____|
|___00349586____|___01294873____|
|___00349586____|___01294873____|
|___00349586____|___01294873____|
|___00349586____|___02394867____|
|___00349586____|___02394867____|
|___05692388____|___00349588____|
|___05692388____|___00349588____|


then I want to create Column C so that I have:

|____ColumnA____|____ColumnB____|____ColumnC____|
|___00349586____|___01294873____|_______2_______|
|___00349586____|___01294873____|_______2_______|
|___00349586____|___01294873____|_______2_______|
|___00349586____|___02394867____|_______2_______|
|___00349586____|___02394867____|_______2_______|
|___05692388____|___00349588____|_______1_______|
|___05692388____|___00349588____|_______1_______|

and so on.

I can use SUMPRODUCT(1/COUNTIF(ColumnB,ColumnB)) to give me the number of distinct values in Column B, but I don't know how to limit that to per Column A value.

Any help is much appreciated

-Niraj