The whole page should become a spinner, whereby the text and boxes rearrange themselves into a Lorenz attractor until spinning is done or error occurs, whereby the Lorenz attractor unfurls with the requisite update seamlessly made and one of those "look at me" blinky circles next to where things were updated ...
... or maybe just a simple spinner to the left of the text within the button (imagining a rounded edge button in my head here, so that the spinner is equidistant from the edge of the button for pi*r of the spin).