Push/Pull gridded surface with curve smoothing

Here's the scenario. Imagine a 2D rectangle measuring 4 feet x 8 feet. This rectangle is then subdivided into a grid of 6 inch squares. I would like to push/pull individual grid points to change the z-value of that grid point. The result would be not only that point z-value being changed but a curve smoothing algorithm would be applied to adjacent grid points. In the end, I want to create 2D sections along the X and Y axis (the 6 inch grid lines). My application is more artistic than scientific so I don't need the curve smoothing to use a specific algorithm as long as I can make it look right.

This is not a civil engineering or DTM surface modeling problem. I don't believe TIN modeling is an appropriate tool for this problem.

The maximum size of my projects will likely be 20 feet by 10 feet with a minimum grid of 3 inches x 3 inches.

I'm not looking for detailed, step-by-step guide to do this. First, I'm trying to figure out if BricsCAD, and what level, CAN do this and then I wan to try it out for myself using the trial version. It seems Rhino (NURBS?) does this - if you're trying to figure out what I'm asking - but I'd prefer to stay in BricsCAD.