Blocking Particles to be rendered outside a mesh

Hey, I have a problem…I sucessfully created a stencil mask to make the particles of a material to be visible only when the particles are inside a mesh(see image), the material used for the particle is Surface/Translucent…However, I need to step this up by making the material a Volume/Post process…but when I apply the custom stencil in the material instead of it to be masked like with the other shader, this simply dissappear completely…the stencil on the first shader is applied on the opacity, on the second in the extinction parameter, any idea?