The easiest way that I know is to save the excel coordinates file as a text file, in columns representing x, y, z, then rename the file to have .pts extension. For example: 0 0 0 1 2 0 2 3.5 0 3 4 0 4 3.5 0 5 3 0 6 2.5 0 7 2 0 8 1.5 0 9 1 0 10 0.5 0 11 0.25 0 12 0 0 saved as points.pts Then create a datum point feature offset from Csys and import the pts file. You can then create a curve through these points, and use this plus other similar curve to create a boundary surface. I hope this helps.
