I'm sorry, but this is support forum for NGUI, and I'm not sure how any of the code you posted relates to NGUI. I can help with NGUI's code, and answer questions, but I can't write code to make some third party code work for you.
If you are trying to replace InputGetAxis stuff with NGUI buttons, then just make buttons and inside their OnPress(bool isPressed) functions record whether the button is pressed or not.