Optimization in the formula box doesn't work

[timor]

Hello,
I have a problem with the Formula box. I want my SL to be a percentage of the daily ATR. Since i cant put a value of for example *0.7 in the Variable, i tried to do it as a formula.

In this picture, i want the SL to be 70% of the daily ATR. It works, but i want to be able to change that percentage in Metatrader. I ticked the box in the Formula window, but i'm still unable to change it on mt4.

Regards

[l'andorrà]

@timor YOu can type the name of the variable manually like this: