Illuminated Keyboard on a 12" Powerbook?

[WinWord10]

Is it possible to install the illuminated keyboard found on 15 and 17" models on a 12 inch and actually have the illumination work? I'm thinking that there's probably a light sensor that the 12-inch model lacks, preventing me from using one, but I want to be absolutely sure. I need to buy a new laptop within the next month and I'm undecided between the 12 and 15 inch base models. The 15 inch is a little more than I was hoping to spend (about 2,200$ with the keyboard I want) and the 12 is much cheaper with everything I need. I really want to show off with an illuminated keyboard though, and it would be very nice if I could install one after purchasing the laptop.

Edit: also I'm wondering if I do get the 15" but don't order it with an illuminated keyboard, could I install one later, or does it need to be purchased with one?

Thanks.