Jonathan,
I believe that you are asking about an incident light meter. I don’t know if it you give you the results your looking for as it would only measure at one spot ( it would give you one temp or the other, or somewhere in the middle ) there is something called the flambient ( flash ambient ) method I think might work better for you. You shoot 2 frames, one with flash and a high shutter speed (to kill all ambient light and to have the “most” correct color) then you the shoot a pure ambient exposure. In photoshop you open them in 2 layers and change the blending option, depending one the one on top, to color ( the flash one) or luminance (from the ambient one). This will give you the ambient glows of lights and windows, shadows, streams of light coming through a window, while having the whole scene color balanced. I use this in realestate photography and learned it from youtube.