Slider and TextBox sharing the same variable

Well,

   Here we are stuck for real. We have an slider, which changes the value of a variable. This variable is shown in a text object. Using 'System--> every tick" the slider's value goes into the text object immediately.

But, if we want to change the value of the same variable through a TextBox as an alternative of the Slider...Thing turns into something impossible. Apparently.

So, we ask for your help!

Here we have the code:

capx

Test