Input in textbox from right to left with comma positioning

Greetings code warriors, I will try to be as explicit as possible, for months I have been struggling with a code without success, I am trying to create a textbox code that allows me to enter the digits from right to left, and in the second digit place a comma automatically concatenated with the unit of "Kg". Below I leave a description of what was requested, I hope someone can help me



Here is the code with which I have been working

Captura de pantalla 2023-01-28 203303.png

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The problem arises every time I press a button in the textbox an event is activated that simulates that I have pressed the button many times below, I leave an image of the error, for example here I press the eight once and see what happens

Captura de pantalla 2023-01-29 030955.png

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1. Are you saying that you are pressing 'delete' after pressing a number key because you made a mistake and want to reenter a new digit.
Post a sample file (with code).

Your whole concept is doing this the hardest way possible. You should have one textbox where you input only numbers, then that is formatted for display in another box.