I finally manged to get user key input, but want some improvements.

I used Firefly's "Is Key Pressed" function with "Timer" function.

I also used "Record Data" function to receive the data 'only' when a change occurs.

It works fine. I hope this helps for those who want to get user input.

I want to improve some though. 

Since I used Timer function, it make the system slower.

If you guys have better solutions, can you share?