Slide the old button image vertically and put the new one in its place. I'd like to be able to compare the before and after. Also, while it's sliding, I'm dis

Slide the old button image vertically and put the new one in its place. I'd like to be able to compare the before and after. Also, while it's sliding, I'm distracted from waiting for the new one, but don't make me wait for the slide to finish if the new image is ready to display.