Sublist Question

Hello,

I have a question which I think is related to sublists...I would like to split a list of points based on their z value.  For example, I have contoured a brep at a desired height and I would like to separate the list of points into several list of points for each contour - is this possible? I was unsuccessful with the Sublist  & Member Index commands.  I have attached a sample definition.  Any help would be appreciated.

Thanks.