Not sure if it is of any interest, I have the code needed to copy Protocol-Buffers to / from cobol in my projects
RecordEditor (
http://record-editor.sourceforge.net/)
Protocol Buffers Editor (
http://code.google.com/p/protobufeditor/)
It would be a case of putting code from the 2 projects together.
The RecordEditor has a copy Utility that can be run on line and in batch;
The Protocol-Buffer-Editor wraps protocol bufffers messages in a RecordEditor wrapper.
Note: The 2 projects are written in java.