Finding the color value of a pixel via UV coordinate in a Material

I’m trying to find the color value of a pixel by its UV coordinate in a material.
I have a material function where I can set the coordinate I want to sample. It takes a texture object and calculates pixel dimensions and travels along in x,y.

However, I want to sample the pixel further along in my material code, when I’ve already manipulated the texture and broken it out to float 3s.

How can I do this? Can I convert back to a texture or alter my material function somehow?
I’m wanting to then use the color output to go into an if node.
Thanks