How to get coverage for dll called by a web service

We have applications set up like this (in order):

ASP
VB6 shim
VB6 ComFacade
VB.NET web service
VB.NET dll
Database

I want to capture coverage data for the VB.NET dll while our QA people run their (manual) tests using the ASP user interface. How can I tell NCover when to start/stop collecting coverage data for the dll?

Thanks,

Mark