calculate sum on footer page (aggregate the total sum on each page)

hi i am new using reportviewer i have a little problem i want to get the total sum in the footer page, i have put this:=Round(Sum(ReportItems("CEIntenas").Value),2) its working but i need that on each page get the sum but aggreage it the total sum of my other pages, i mean i want to cumulate my sum for example in my first pagei have a total sum of 100 and in my second page the sum of this page begin from 100 i hope anybody help me