Hi Lemo, normally you would use Fillet to smooth out a sharp edge where 2 surfaces are meeting.

Check out these videos: http://moi3d.com/1.0/docs/tutorials.htm , they cover using Fillet.

But it is a little hard for me to understand your shape just from a description, if Fillet isn't what you need, could you please post the .3dm model file here as an attachment? That would let me examine the model and come up with a suggestion.

- Michael