In the "purchase.report_purchaseorder" report I want to get  the sum of all order_lines of the first page (wich i would do with js) and show this sum as the first entry in the table on the second page. How am i able to do this or is it impossible, becouse i can't get the current page?

Link to a picture witch should descripe it a little better, at least i hope it does.

https://www.dropbox.com/s/vmneo880ze7ex74/Purchase Order Report.png