I am trying to design an infrustructure that I plan to use in modal dialog windows that will be used as edit pages in my application.
Content is always read-only in a regular window and edited in a modal dialog window (AKA edit window).
I am looking for the right way of implementing the interaction with the server in the edit window.
An edit window is always composed of 3 frames:
* top frame for a header strip
* a middle frame which contains all the components of the edit window (text controls, buttons, etc...), AKA main panel
* a bottom frame for placing action buttons such as: "Cancel", "Save"

When the user clicks on "Save" button, the content of the main panel should be sent to the server where the database will be updated.
However, some of the settings that the user can play with in the main panel may require interaction with the server (for example, the user can upload an image from the local file system. Once the image is loaded, I want it to be displayed in the main panel after being manipulated in the server).

I am looking for a smart way of implementing this.
I thought about adding an additional invisible iframe in the edit window which will be responsible of interacting with the server. Whenever a user adjusts a component in the main panel which requires an interaction with the server, I will perform the interaction via the invisible iframe; sending the necessary data to the server in a form that will be hidden there.
Once data is returned to the iframe from the server, it will communicate with the visible main panel and update its apppearance on the client-side.

Can anyone think of a better solution for the problem.
I am trying to prevent the entire edit window from being redrawn everytime an interaction with the server is needed.

thanks for the help