How to do a voronoi in a custom 2d shape,..???

Hi,

Does anyone know how to make a voronoi in a custom shape, I mean when i use the voronoi command in Rhino or Grasshopper, it is asking me for boundary points, but wat if i need a voronoi in a closed curved line,..?? I tried dividing the curve into many segments and select those vertices as boundary point but the computer is going blank to do that,..
Is there any other way to just select the "internal points" and "Boundary line"(not boundary points) and obtain a voronoi in that perticular boundary line/closed curve,..???

Thanks a lot