Yeah you can affect only a certain layers or groups below the adjustment layer. Either by scripting, or by a bit of creativity.
It's kind of complicated to explain, but the functionality goes like this:
- you have layers you want to be affected, and others you don't want to be affected.
- group those who should be affected, and above these create a new layer and apply the current image (image>apply image). Hide the folder (so that you can keep the raw i.e. source layers within it untouched.) Create your adj. layer above the layer with the applied image, and merge them.
So, whenever you want to create an adj. layer that should only affect a certain group of layers, apply an image of these layers, hide them, create the adj. layer above the applied image and merge both last.
I hope I explained myself, otherwise let me know and I'll try to be more precise.