I have an image of a helium balloon appearing from a gift box on a ribbon. What I'd like to do on a javascript event (such as hover over a radio button) is make another balloon appear to be coming from the same box in addition to the first one.

I could work this out myself if I simply used a new image for each rollover, but is it possible to somehow 'cut' a section of the original image and display it over the top at an angle? There are hundreds of existing images on the site so this would be an ideal option rather than creating several new images of each one.