How to auto-focus Nikon d3100 during video?

Hi, so I just bought a used nikon d3100 a week ago with the 18-55mm lens. I love the way it takes pictures but i'm trying to shoot videos of myself and it won't auto-focus! I have to do it manually or have someone else do it. I have in viewfinder, auto, VR is on, and it won't automatically focus when i'm taking a video! Is there a way to adjust a setting on the camera so it will? Or should I try returning the camera because it's bad?

This article has suggestions and limitations of autofocus for the D3100.
http://www.dpreview.com/...ond3100/15

I don't think you can with this camera. Only a select few dslr cameras have that feature. Besides, trust me, you don't want auto focus during video.

Learn how to twist the focus ring and use manual focus - the only real way to shoot video anyhow.
I know, I did a career in broadcast television video work and never did I have a camera with auto focus.
Put simply, it doesn't work.

The dSLR was never meant to do video which will always remain as just a feature. Hence, there's not much video control on it. The D3100 does not have autofocus during video. Your options are to manually focus the lens (make sure you set it to manual focus before doing so) or walk to follow your subject and keep it in focus.