The mathematical expression for a given boundary defines a function, which can be any function of the system atomic positions. The functions for a cell (one function for each boundary) are defined by the user such that when the system is inside the cell, the boundary function is negative. But if the system ever crosses the boundary, the value of the boundary function is positive for that system configuration. Such custom mathematical expressions make it straightforward to define Voronoi cells and boundaries in high-dimensional spaces. Examples are included along with the plugin that show how the collective variables defining anchor points can be distances, angles, or absolute positions between atoms or any groups of atoms and more.