Button to register a pour on the "Fullscreen" page

Just discovered Kegbot today. Wow.

I do not have any flow sensors or anything else to that effect.
Through the admin panel I can register my mates’ pours - however, would it be possible to for example create a button called “0.5 liter” and one called “0.33 liter”. Once pressed it would register a pour.

Would greatly appreciate any tips and or tricks that could help me achieve this.