possible to refresh divs outside of an iframe? (general web dev question w rails-y flavors)

I know this is a general question, but there is an aspect to rails dev
that I hope makes it appropriate to post here...

I'm building a FB App for a client using the Facebooker plugin.
Because of the way FB restricts file uploads, I had a task to enable
file uploads that required me to put an iframe in the FB canvas page
for a form where I have the file_field and do the upload. That's
working well now.

But, what I want to do is refresh a couple parts of the page after the
upload completes (to indicate that the upload was successful w a flash
msg and maybe display the thumbnail of the image uploaded).

I've tried to display set the flash from the controller action that
receives the post of the upload, but what I've found is that the flash
msg doesnt show in the surrounding canvas page around the iframe. I
guess this is because the controller-view interaction here is for the
iframe, not the whole page... right?

Also, I dont know how to get to the divs in that canvas page either to
refresh them from the controller action.

So is it possible to 'address' divs in a containing page around an
iframe, in general, and are there any twists with rails that make it
possible or impossible?