creating groups of faces for openfoam boundary conditions

I finally refined the mesh doing this:

1) I create a submesh with the edge of the source face I want to refine.

2) I create another submesh with the equivalent edge in the destination face and take 1D Projection as algorithm and then I put the edge in step one as the source edge. That way it seems to work properly.

ok, I'll try to do something when I'm writing all this down as I couldn't have done it without the help in this forum