Photoshop :: Clone From One Layer (photo) To Another Layer (photo)?

I'm trying to clone from one layer (photo) to another layer (photo), and simply want an exact pixel-to-pixel replacement.  For instance I'd like to copy pixel (10, 20) from the first layer to pixel (10, 20) on the second layer.
 
I've found that I can set the upper, left corner of Layer 1 as the "source" (using Alt+click), and then go to my "destination" layer, and click on the same upper, left location, and then subsequent click-and-drags will then be aligned, but that is not an elegant process.  I'm assuming that there's just a button click or option that I'm not aware of that will make all of this much simpler.
 
PS: I'm using PS CS5