Capsule works like many spheres between its start and end points, so maybe you need to use few sphere masks along a line between player and camera locations.
But in case you need to hide whole floors above player, you should use something like
Clamp( 0, 1, dot( (world position - player location), (0,0,-1) )
It will give you set of 0 values above player location, and >0 below it.