Lauch animation at certain position Y

Hello guys,
I am trying to launch an animation when we are at a certain position Y.
For example, when we are at Y=350 → I want such an element to appear with a certain animation that lasts X seconds.
I only found solutions so that the animation is modeled with the scroll (that basically if I don’t scroll it doesn’t continue to play.)

I don’t know if I’m clear, but I’ve been trying to do this for a long time

thank you very much