using VBA to update a pivot table data source

Hi, I am a newbie to VBA trying to learn more but at the moment I am just doing basic macros. I have created a simple pivot table and started with basic data for week ending 25/5/2015. I added a button and assigned a macro to it so when I add the new sheet to the workbook named 01/06/2016 or 08/06/2015 and click on the button it will update the pivot table to the current sheet I want. This is just a basic example as I need to do this with a bigger pivot table but with the same concept. Any guidance will be appreciated.