The OffsetSurface TML is included in the TBC 5.0 install but I have updated it to include support for adding a clipping boundary while it copies the surface. The clipping boundary is optional. If you download this zip file, make sure you unzip it in the same folder as the macro installed with TBC (C:\ProgramData\Trimble\MacroCommands\Trimble)
I received the error below when trying to offset the surface in the attached vcl.
Error with Offset Surface