I have a 4 level Drill-down dimension, when i select multiple values, how to calculate sum of sales for that respective selected dimension values.

For example:

My first level is State- I will select one or multiple states - when i select one state i need sales for that sate and if i select multiple states then i need sum of sales for that state. But when i drill down with multiple states selected to next level which is city and select multiple cities then i need to show sum of sales for that Selected cities.

Thanks in Advance.