Questions in EvDRE in BPC

Dear Experts!

I am new to BPC.

Can any body help me in creating multiple EvDRE Grids. And i have amounts of year 2007 & Year 2008.

How can i calculate Variance.

And how can i connect multiple EvDRE grids one with another EvDRE grids.

And how can i place Buttons and how can i assign task to these buttons.

Please help in Customize EVDRE Grids.

Thanks,

Satish