If you're only smoothing a few faces, you can use this process:

1) select the faces you want to smooth.
2) Choose Edit Polygons>Extract. DO NOT move any faces. Extract takes each face you selected and makes it a single object.
3) select all the faces you just extracted and choose Polygon>Combine.
4) select all vertices on the new object and choose Edit Polygons>Merge Vertices options box. Set the value to .01 and click "MergeVertex."
5) Select the object and choose Polygons>Smooth.
Select the object again, then select your original model and choose Polygons>Combine.
6) Select all vertices and choose EditPolygons>MergeVertices again.
7) Your done.

When choosing faces to smooth, you don't want them to have many jagged edges anywhere. You may have to do this process on a section of faces, then another seperate section of faces, then combine them to get the correct effect. This process might not work if your mesh is not at least somewhat smooth already. I would recomend saving before you do all this, then if you don't like the results simly reload the file. I used this method for the smoothing of my helicopter in the 3D challenge competition and it worked out pretty well.