Photoshop :: How Can I Use Auto Color On 2 Layers W/out Flattening The Image?

I've been taking photos with a homemade lightbox which includes a white background and I typically have to go into photoshop to make some adjustments to get the background pure white. When I'm snapping a photo of an all white object against an all white background, it looks rather nasty if you use the auto color tool.

So from my understanding auto color uses the lightest white and the darkest black and the reason the white/white scenerio doesn't work it because of a lack of black. So to combat this I've been creating a new layer and adding a little black with the rectangular tool and filling it with black. Now, I'd like to be able to delete this second layer once I've used the auto color feature but can't figure out how.