Render selected objects only : render just the selection (but not other objects)

Hi,
I have an idea : it is possible, when we enable the “Render selected objects only” (and disable the “clear render view”), to do not clear the previous render and render just selected objects ? Like an “update” of the image.
For Vray ? (and Vray RT)
It will be like the region render, but the region is the “alpha” of selected objects.

I don’t know if i explained well.

Yes, it is on the “to do” list.

Best regards,
Vlado

Same idea I got some times too. Could be great, if “render selected objects” would allow to render a scene, where the rest of the scene is transparent (alpha). So, I could easy update an “old” rendering at Photoshop if a client want to get a material changed only, without to rerender the whole image. At the moment I use the mouse tracking to focus the rendering to my needed objects, but this is quite time consuming.