Change the state of an object when typing in a data entry box

I'm trying to change the state of an image with each character that's typed into a data entry box. The user needs to be able to type any combination of 4 characters and then press the enter key to advance to the next slide.  The aim is to move the image forwards with each character that's entered and backwards with each character that's deleted when pressing the backspace key. I can get the image to move forwards and backwards using the keyboard, but not with a data entry box on the slide. Is there a way of doing this using a data entry box?

I've attached my demo file.

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