HX711 removing tare with button

As the tittle says, how to remove tare on button? I use HX711 with load cell and Uno. Everything works fine, but i would like to add a few things to make a scale. The idea is when i put a, say, dish on it to press a button and set a value to 0. When i add sugar it will measure only sugar. Then i will press it again to set it to a 0 so i can add other things.

I use this library. I modified this example a little bit but nothing much.

It will need to be in a loop. But, if i check if button is pressed and set scale.get_units() to zero, i am not sure if i mess up calibration which is in setup above. Any suggestion would be nice.

When you press the button, set a variable tar to the current measurement. Then display the actual reading minus tar.

Pieter