Default How to turn softkey-backlight on/off without rebooting?

Hello
Actually I'm searching for an idea how to turn on and off my button backlights on my Samsung Galaxy ace2.
I would like to have an script, which, when it was run with tasker, turns of the backlight immediately.
It would be nice, to use the BLN feature of my Kernel and still being able to turn off the normal backlight when using the phone actively. Each time I will turn on the screen then, tasker should run the script to turn off the backlight.

Thank you for your help )
Devices:
Samsung Galaxy 5 (two devices, one is completely disassembled) - CM10.1
Samsung Galaxy ACE II - CM11