I used the following piece of code in the web.config in order to maintain the scrollbar position after a server postback:
You can do what you want, but it will need to be done client-side with something like jQuery. The following tutorial uses jQuery to determine the value of the scrollbar within your GridView control and then restore that value every time the $(document).ready
function is called. In this manner your scroll bar will be reset to it's position before the postback as you wish.
Easily maintaining scroll position in GridView using jQuery