Retry a file upload?

Hi,

In my program, using Ext 4.2.0 and PHP, I have a form where users can upload a file. This is using the Ext.form.field.File component. When the file is submitted there is the possibility that an exception may be raised server-side. This could be, for instance, because the program wants the user to re-submit their password to ensure that they are who they say they are.

When this happens, I want to be able to put up a messagebox asking for the user's password and then retry uploading the file. This works fine with normal AJAX requests since I just resend the request. However after the unsuccessful file upload the file field becomes blank and I can't re-submit the form without the user re-selecting which files they want. Is there any way around this?

Thanks!