LostFocus event for TextBox - how to make it work

Hi,
I am not an expert in VBA so I am struggling to make my form work like I want.

I would like to have a textbox on a form. In this textbox user will enter weight of item he wishes to add to database so I want to format text in this box as " #.0 kg".

I wanted to use LostFocus event but I am unable to make it work. It seems no to occur, my code has no effect.

I am attaching my file. Please help me to understand what is happening.

Cris