To check if a button has been pressed on the page, you can store when the button has been pressed on the page using JS in the page's html. While also checking this value from C2 every tick, and if true, set to false. This seems like it should work, but I've never tried.
To update a text field you can again use the execute JS action, manipulating the page as if you were writing inline JS.
Please note I've never tried to do this myself so I do not know if it will work.