Download the Max 7 file: FXdisappearingAct.zip

This is a sphere passinh through an object and completely disappearing as it does so. It also emits particles at the point where it's vanishing. I'm using a script controller to keep the slice plane of a Slice Modifier on the sphere aligned to the hoop object it's passing through. This way you can animate the sphere, or the hoop, rotating and moving around in the scene and the sphere will also disappear as it's passhing through the hoop. Try moving the hoop around in the viewport to see what happens. And then there is a Volume Select modifier on the sphere also so that the particle can be emitted from the selected vertices as it passes through the hoop.