Load control dynamically on scrolling

Hi Guys, As I am new learner in AS.NET 3.5 with C# , I am facing one problem . I have div in my form which have user controls in which each control laoded with an image. When I run the application I use a for loop to load the images at run time (Adding user control dynamically ). This way is efficient when I have 10-20 images. But it will take lot of time when there is 1000-2000 images to load in each user control individually. What I want is that is there any way that will load the control with images as I scroll down in the div?? It is similar to those e-books concepts. We have thumbnails at left side (Image) when we click, it will show the whole page in right side. Waiting for positive reply