[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
[TABLE="class: grid, width: 500"]
<tbody>[TR]
[TD]Month[/TD]
[TD]1[/TD]
[TD]2[/TD]
[TD]Grand Total[/TD]
[/TR]
[TR]
[TD]Customer 1[/TD]
[TD]4[/TD]
[TD]4[/TD]
[TD]4[/TD]
[/TR]
[TR]
[TD]Customer 2[/TD]
[TD]3[/TD]
[TD]3[/TD]
[TD]3[/TD]
[/TR]
[TR]
[TD]Customer 3[/TD]
[TD]3[/TD]
[TD]4[/TD]
[TD]4[/TD]
[/TR]
</tbody>[/TABLE]

I want to used [Calculated Fields] show like below

[TABLE="class: grid, width: 500"]
<tbody>[TR]
[TD]Month[/TD]
[TD]1[/TD]
[TD]2[/TD]
[TD]Grand Total[/TD]
[/TR]
[TR]
[TD]Customer 1[/TD]
[TD]4[/TD]
[TD]1[/TD]
[TD]1[/TD]
[/TR]
[TR]
[TD]Customer 2[/TD]
[TD]3[/TD]
[TD]1[/TD]
[TD]1[/TD]
[/TR]
[TR]
[TD]Customer 3[/TD]
[TD]3[/TD]
[TD]2[/TD]
[TD]2[/TD]
[/TR]
</tbody>[/TABLE]


What should i Used Logic in Calculated Fields


Sorry about my English