Controlling a non-Apple monitor's brightness using OSX

I have 2 Dell 21.5 inches monitors that I like except for one thing which is controlling the brightness. They don't have anything that will detect the lighting in the room and therefore, I have to constantly keep on adjusting the brightness to suit the room's lightning. This is annoying because 1. its 2 monitors and I have to change the brightness on each of them 2. They're a button that I have to keep on pressing repeatedly and its not a 1-10 scale but 1-100.

The 2 monitors are connected to my Macbook Pro through thunderbolt to HDMI. I'm not sure about HDMI but I know thunderbolt would carry a brightness adjustment since you can do that with the Apple Cinema Display which connects via thunderbolt. Any suggestions on how to do this? I know the possibility of being able to control the monitor's brightness using the F1 and F2 keys is very low but doesn't hurt to ask for other ideas.