Render to Texture question

Using this script

Is it possible to display what happened one frame or more earlier?

I’m trying to develop a motion blur that will be ‘soft edge’ or blurred via nodes. I just need to be able to display different points of time.

I’ve almost been able to get blender to a state of not needing 2d filters. I’ve node-coded bloom, a simple depth of field, and dirty lens flares which all work super fast. If anyone could help with my question, I would appreciate it very much.