Find a data location in scroll form

I have a array list of data by which I show a graph on a form, this form has a scroll bar and I design a feature that customer can show those data in more than one page as well. So by scrolling, customers can scroll their graph to left and right side to see all graph based on array list in more than one page. when I scroll my form and divided my data f开发者_Python百科or showing on 2 pages or more, I'm going to have a graph that when I click a mouse on that graph I can find real data location in array list correctly. I don't have any problem when I have one page because for each location I can find exact location of data in my array list as well because there is a equal relationship between my page and my array list location. But in multi pages when I scroll graph in different position, I can not find the exact data location based on screen position. When I click a position in my graph and move it to left side or right side I want to be able to change that data in my array list as well. Could you give me a clue to solve my problem please.