Disable typing image url, force upload from server only

Hi All

Hoping you can offer some help here please because I can't seem to find what I'm looking for in the docs.
http://docs.cksource.com/ckeditor_api/s ... oader.html

When you click the image icon in the tool bar, ther image upload dialog opens.

I need to disable the ability to actually type/paste a URL into the URL field(s). I need to force the user to choose a file from the server only?
(server browse already implemented, not the issue)

Any and all thoughts or suggestions will be very much appreciated.

Thanks very Much
U