Photoshop sprite animation

Stinger88

OK, so the other day I was watching the Mojang Mojam2 and one of the dev's was creating some sprite animations using photoshops animation/timeline feature. While he was editing the sprites he was able to have the animation looping constantly in the navigator window and the animation updated as he edited it.

How do I do this? Is it a plugin?

All I seem to be able to do is run the animation in the navigator but I cant edit any layers while the animation is running so I have to stop it.

Any ideas?

Thanks