NEED HELP: Screen Effect - Expandable Coloured Grayscale

So, I tried to create a Coloured Grayscale Screen Effect, and I had in my mind that the Grayscale Screen Effect should expand from the center of the screen, in a radial way, and back.

However, I’m stuck on thinkering on how I could do that. Any help on that?

Here’s the graphshot of the Post-Process Material Blueprint.


Plus: Second Issue:

Sky is not reacting to my PPSE (Post-Process Screen Effect) Grayscale. How I can fix that?