shutterman you need to zoom in to fill the viewfinder with the colour checker under the same lighting conditions then when you take the captures into your program, you set the white balance using the 18% grey scale patch. They you select the other images and apply the change to those images.

That is the theory of how to do it. Problem is I don't know exactly how Photoshop does it as One I don't use Photoshop to edit my RAW images I use Capture One, Two I don't have a Nikon so can't guide you on that one.

The above principal that I described is the process.