How to preserve Checkbox status while paging

I am using ur code in my application 

http://www.aspsnippets.com/Articles/Preserving-state-of-Checkboxes-while-paging-in-ASP.Net-GridView-Control.aspx

in your code ur gridview is loading on page load but my gridview is loading on button click event 

Can you please suggest me how i will use ur above code in my application on butting click event 

Thank you

Sandy