Would a solid suffice? (see below my signature - feel free to let me know if that's accurate enough).
I believe the trick is understanding how to use the command...plus, your example was planar, so that removed much of the guesswork - no segmentation to the splines & degree of 3 maximum.
Now, once you get the dialog up, expand all the choices. You'll see the degree & segment options. I immediately change those to degree 3 & segment of 1. Turn on Preview & leave the rest as-is.
Now we're going to try & pick the extreme corners of each FACE we're trying to create using the corners of the faceted model for reference. Start picking at the corners and after you see a line (should be after 2 corner picks), click Accept Points. Start at the corner you last picked (or the end point of the line created) and create your second line. Rinse and repeat until you see 4 lines - accepting each line as it is created. You WILL get an error that it cannot create a surface. Ignore this until you have a closed bondary for a surface. Once you do, you may have ot rotate the model to see it. Create 1 face (surface) at a time, possibly having to use Trim here & there as in my attached example.
I figured this out by reading the documentation and trial & error. Surfaces with more curvature will be tougher to do. You're not going to get an EXACT match using this command, but if you're patient, you should be able to get it pretty darned close.
Hope this helps.
Tim Flater
NX Designer
NX 7.5.4.4 MP2
WinXP Pro x64 SP2
Intel Xeon 2.53 GHz 6GB RAM
NVIDIA Quadro 4000 2GB