Turning off the laptop monitor when using an external device.

I regularly use my laptop to watch films on my TV. To do this I extend the desktop onto the TV and use VLC media player on this extended destop. This allows me to still use my laptop as normal. I want to be able to turn of my laptop screen (or just the backlight) as it is distracting when trying to watch the film. If I switch from the laptop to tv using crt/lcd (Fn - F8) on mine it makes the tv the main desktop which I don't want to do.

I have downloaded mon_off (http://www.softpedia.com/progDownload/m-off-Download-115077.html) but this turns off both the laptop and external monitor. Is there a program that will differentiate between the two or any other work around to my problem.

Thanks in advance

Rich