How can I use the rendered material result in a blueprint as a texture?

I need to do some calculation which is heavy for c++ and is time consuming.
so now I am doing it via materials and use the power of GPU which is indeed very fast. the problem is that after the rendering is finished I have my data as a texture and I need to access it via blueprint. is there a possible way to do this and making sure it always happen after GPU finishes rendering the material ?