Yes; I did consider copying the same expression on the Z, but assumed it would mean more computing!?
NOTE: The expression works as intended if I place the script slider on the null.
The null allows me to place/move the square easily on the comp for now. I plan to fill up the screen with the squares. Kind of making it appear like a vortex. Once in place, I’d delete the nulls. Wanting to recreate something like this.