Message passing from PSCP in -gui mode.

First off, my apologies if this subject has been covered before but I
can find no mention of it anywhere except in the source code for pscp..

My intention is to write a windows service that will be a front-end to
PSCP and I would like to use the message passing features of PSCP to
inform my service as to the progress of file transfers.

Are the messages passed documented somewhere *other* than in the source
code?

I can probably glean what I need from the source, but what gets sent
and when is rather disjointed in the source.

Thanks!

.