I think you would have to build a Wave Gadget.  Would be pretty cool because then you would have the functionality of the playback scrubber to see what your sales graphs looked like at any point in time.<p>It would probably take a couple of days to open up a service on the server-side, and to write the client-side graph generation.  Not sure if a Wave Gadget can pre-emptively fetch data without user interaction though.  That might be a killer.