How to find growth %

Hi all,

I had the following scenerio. I have to build a query for the following..

year : April(sales) : May(sales) : June : .........May(sales): total : Avg : Growth %

2003 : 20....................................................40............:100..: 20....................

2004 : 30......................................................50............:120..: 20.........30%......

2005 : 40......................................................60............:150..: 30.........50%......

Please help to find out above scenerio.

Thanks,

James.