Loading in previous renders when batch rendering

[Kelv]

Is it possible to load the previous render of a render layer whilst using batch?
I'm looking to isolate new geometry by using render mask and then render over the top of previous render (so don't have to re-render everything, just patching in).

So for example, I'd have the following render layers:

- render_layer_one
- render_layer_two
- render_layer_three

Batch loads in previous render of 'render_layer_one' which would be 'render_layer_one.jpg' (the loaded jpg is same name as render layer), then renders the new masked selection over the top of the previous render, overwrites the loaded in image, then loop through other selected render layers.

Is this possible?
Thanks for reading.

[SonyBoy]

Why don't you just do it in post? This sounds like an unnecessary headache.