Spline objects are the general form of shape objects in Max studio. but max-script doesn’t provide a direct tool to generate this kind of objects in the scene like what we do by simple scripted plug-in.the only way is extending the existing  type of shapes. But in this case you will not be able to save the parameters and properties of the instance such as number of knots and position of vertices. To deal with this situation I used a simple trick.

We create a helper object attached to a simple spline shape. The helper object can save and manage the parameters of spline shape and also can generate a new shape in demand. Therefore we’ll have all parameters in modify panel when the helper object is selected.