It is also possible with a Sheet Worker. I did that for the Savage Worlds Tabbed character sheet. I don't believe you can use a real button, but I used a checkbox with a span to make it look button-like. Then you'd set up your Sheet Worker to watch for a change in that checkbox, and when the specific change you're looking for occurs, then you use setAttrs to set all the values of the fields to 0. You'd likely want to change the value of the checkbox as well to "reset" it. D'oh! Sniped by Brian.