Parameters - Hierarical Database

I need to report againist hierarical database where the user may select the parameters until the lowest level or stop in the middle. If the user select until the lowest level, then, I can simply call report with all the values. But, what if the user stops in the middle? Can somebody help me explaining how to pass the parameters in the above case? Can someone email me so that I can send them a document explaining the hierarcy structure of the database againist which I am reporting.
Thanks
Raj