Why? AdvancedTextBox and Button

HI,

I would like to write in disable AdvancedTextBox a letter when i use the keyboard.

I made some test but if i use a button to autorize the keyboard, "Set text" don't work.

And with a personal "Sprite button" it run.

i don't understand why !

Here is a smal capx to illustrate:

dropbox.com/s/36z68ww7ulg8eky/mut_essai.capx