Triangles are planar, so you can use CreatePlanarTrimSurfaceDLL.
myBody = myPart.CreateNewBody
ret = myBody.CreatePlanarTrimSurfaceDLL(vPt, Nothing)
ret = myBody.CreateBodyFromSurfaces
where vPt is an array of doubles representing the xyz coords of 3 points (i.e. an array of 9 doubles).
Thank you very much, this reply helped me a lot.
There is still a liitle problem here, after I use ret = myBody.CreateBodyFromSurfaces I get false, even though I get the surfacebody created corretly, will this matter?
I'm not sure, but maybe that is indicating that there was more than one, disjoint surface body in the result. Perhaps it discarded a small portion of the mesh that was not joined onto the rest?