Hierarchy level change sort order in matrix table

Hello... this would be great if we can get this feature... If a solution to this is out there already please share.

[See Screen shots below]
1st I have a matrix table with items that have been sold to my customers, this is sorted in the amount sold column to see what Customers and items have the greatest sales value... From top Customer, down to the least for all my customers. However I have added a drilldown with month and year and require these months to be sorted not in sales value order but now in month year order????

Is this possible? 

So just to explain further I can see my top customers based on sales value (sorted in descending order - perfect), then I can drill down and see their products bought... this is also sorted in sales value order (perfect). Then I can drill down further to month year but this is also sorted in sales value order and not month year like I need it. 

Would like the ability to change the sort order on drill down... This would be great!

First Level in Hierachy

Second Level in Hierachy:

Third Level in Hierachy and this is where I need help... the sort is using the previous sort order and not my date order:

Trying to get Jan, Feb, Mar, etc

Thanking you in advance
Mark