Dear Alexis,
The upcoming version of Blue Kenue has this ability.
You cut out a section of an existing mesh, use the resulting "island" as a fixed boundary for a new submesh and then merge this new submesh back into the global mesh.
The new version is still in BETA but if you contact me offline at This email address is being protected from spambots. You need JavaScript enabled to view it. I'll make this new version available to you.
Cheers... Martin