what is the best way to implement ?

hey

i'm trying to implement keyboard based on inputs(only arrows)
i need to create buttons (all the letters) that will be "lighted up" one by another when the user press right / left / up / down
after he will press ENTER the program will get the specific letter that will be shown in a text box and in this way
he will be able to write only with the arrows.

how should I implement this in the easiest way ?

What have you already tried?