You can, but you don't! You USE yourtable TAG yourtag DESCENDING and get the result you want!

index on khubaib tag khubaib
set order to khubaib descending

If you REALLY must:

index on -khubaib tag khubaib

>Dear all,
>how i can set the data DESCENDING
>index on khubaib tag khubaib&&&1,2.........10
>i want to 10,9............2,1