[Calculated Fields] how to Get Count Product more last month

[nanuutm]

i want to used [Calculated Fields] on Pivot table to show customer buy number of product compare last month

Ex

Month 1
Customer 1 Buy 4 Product A B C D
Customer 2 Buy 3 Product A B C
Customer 3 Buy 3 Product A B D

Month 2
Customer 1 Buy 4 Product A B C E
Customer 2 Buy 3 Product A B D
Customer 3 Buy 4 Product A B C D


In pivot Table i used [Count Distinct]

Result

Month	1	2	Grand Total
Customer 1	4	4	4
Customer 2	3	3	3
Customer 3	3	4	4

<tbody>
</tbody>

I want to used [Calculated Fields] show like below

Month	1	2	Grand Total
Customer 1	4	1	1
Customer 2	3	1	1
Customer 3	3	2	2

<tbody>
</tbody>

What should i Used Logic in Calculated Fields


Sorry about my English