Detect Backspace Key Press on Touchscreen Keyboard With TMP_InputField

Hello,
I’m developing a verification-code like submission screen for my mobile project. I have 4 TMPro_InputFields side-by-side and when you enter a number to one of them is gets the value and activates next input field. Same applies in reverse when deleting a number from one of them.

The problem is; If someone presses Backspace key on their touch keyboard and meanwhile text of InputField is empty, I can not get any event. I must activate previous InputField in that case. Since text value remains same, OnValueChanged is not triggered. I tried many combinations (like Input.GetKeyDown at Update) but none of them worked with Touch Screen Keyboard. Can you help me?