It would great if there was a way to allow areas in the photo to be deselected so that they are bypassed from processing. This is separate and distinct from subject selection. For example, I had a photo with a setting sun in the background that had a nice red/yellow/orange color. However, after processing it through Topaz, it blew out the inside of the setting sun making that part of the photo unrecoverable.
So, what product are you referring to?
Sounds like you need to use a mask, but difficult to say exactly how without knowing which product/app you are using.