sorting not working on drill down - cognos 8

[Manu0521]

Sales Rep in rows
Qty as Measures and
I have two products A and B and I am Doing having a Total column and this is nested with respect to ytd in columns.

Qty   Product A      Product B      Total   
SalesRep   YTD   PYTD   YTD   PYTD     YTD1   PYTD1
A            100   200   150   200          250   400
B            200   100   150   200           350   300

I have used order(salesrep, tuple(total,ytd1,qty) ,Desc)

And sorting works fine..

I click on sales rep and drill down to next level which is customers, but here the above sorting doesnt work..
How to achieve this.

Thanks,