ok, 3 points define a plane. short of sketching on a datum through those 3 points and connecting the dots, what's the fastest easiest way to construct the surface?
Are you wanting to repeat this surface feature repeatedly?
This is my case, so I created a UDF(flat surface feature) that refrences only three points or vertexes. Then, I created a mapkey that reads in the UDF and automates all picks but the three vertexes.
The result: I hit the mapkey button and pick three vertexes. (a merge can also be added to the mapkey if you are quilting).