Generate boxes from a random number from a list of points

Hi, 

I would like to create a number(random number) of boxes which take random points from a list of points as its origin. the sizes of the boxes are also be random. I wrote some simple operations (the c# box in red) but it does not work. perharps the logic is wrong too. There is also some problem in converting from int to Rhino.Geometry.Interval too. I attach the file for rhino and gh here. 

Thank you very much :)