Assign new SLP Window to existing images

We have a backlog of SLP images and would like to change the SLP Window assigned to the back logged images. Is this possible? If so, how?

We have an SLP window that opens at 5 PM and closes at 7 AM. We would like to either temporarily change the SLP window or create a new one. That part is easy but we need to assign the modified/new SLP Window to existing backup images - not new images.