fileupload to hidden iframe (cursor changes to spinning wheel)

[David Durham]

I have some code that POSTs multipart form-data to a hidden iframe
when a FileUpload changes. My issue is that the cursor changes to a
spinning wheel while the post is processing, even though the post is
to the hidden iframe. Is there a good way to prevent this behavior.
I noticed that gmail, for instance doesn't show a spinning cursor
while files are uploaded in the background. I'm wondering what the
magic is.

Thanks in advance,
Dave