Custom Character sheet question

I'm putting together a custom character sheet for use with my gaming group's preferred system. A little bit of background information: The system uses a HP grid that has multiple damage levels that can be applied to the grid. The damage types and the symbols we use for them are as follows: undamaged O blunt / lethal X critical * Now the question/problem: Because of the interactions between damage types, where more serious grades of damage overwrite lesser grades, I'm trying to figure out a way to create a table or array of buttons as the HP grid, wherein a left click will progress the grade of damage to the next one by changing the symbol, and if possible, rightclick regresses the grade of damage by one grade. I ultimately want to know if it's at all possible to create a setup like this using custom character sheet editor on Roll20, and if possible, how I might go about doing so. Thanks! Note: I've also posted this question to the Roll20 Reddit , as I check Reddit more frequently than Roll20 forums.

We can't capture rightclicks, so degrading damage trough that won't be possible. So you'd need to add in a reset field - when you click it it would reset the the most serve damage to zero (first resets critical, then lethal, then blunt). So if you'd like to reduce critical damage, you first have to reset it then set it to it's new value. It gets worse when you want to reset lethal but already have critical, then you'd need to reset both and set them again... Here an example for above. Note that you have actually 3 damage pools (blunt, lethal, critical).

You could also use a loop of radio buttons.  Here's an existing example . Once such a radio button group has focus (eg, you clicked on it), you can also change its value using up/down or left/right arrows.