What does "<MSHelp:link ...>"

Okay, I know what it should do, but I would like to know *how* it is or
can be done ;-)

I do not simply want to show such pages, extracted from HTML help files,
but I also want to update them before display, and react on clicks. The
whole thing should allow the user of VS or BDS to update the shipped
online help, with e.g. annotations, references to examples etc.

What can I do to make such pseudo-links work like true links?

DoDi