$TX.$TOUCH_ENB variable field protected

Hello fellow members,

I'm trying to disable the touch screen capability as stated in this post : https://www.robot-forum.com/robotforum/fan…61840/#msg61840.
My problem is the $TX.$TOUCH_ENB is field protected and i can't change it (tried it also in controlled start with the same result).
There is probably something i miss or i do wrong but i can't find what it is.

Anyone know anything about this issue ?

Thanks