Virtual Provider - Select data by two tables

I have a requirement to build a virtual provider which should use the date variable values as input from the user. Based on which I need to write a select query (probably using function module) on a couple of DSOs and aggregate the data in the database. Then should pass the data back to the OLAP layer.

Can someone explain:

1. How to pass the selections from the query back to the virtual provider

2. Where should I write the select query in the Virtual provider, Is there a BADI available to do this

3. How do I pass the data back to the OLAP

4. Will the aggregation adjust automatically in Virtual Provider according to the query drill down

Thanks in advance

Regards,

_Mhel