Keynote - Changing multiple slide backgrounds at once

Is there a way in Keynote 08 to change multiple slide backgrounds at once? I'm doing slide show and using custom background images on slides. Sometimes I'd like to keep my text, but change my background images for multiple slides. Right now I have to select each slide individually, click on the image in the slide, hit Delete, then drag new image into it, then do the same all over again with next slide. Is there a way to do say 5 slides, or 10 slides, at once?