how to exclude untested code from the coverage report?

With NCover 1.5.5.0, is there a way to exclude untested classes from the coverage report?

We have a commons project, whose src code is compiled into our 3 main projects. For test purposes we compile a common.dll and run ncover using common.test.dll. Coverage shows as about 90%. For various reasons, we compile the common src code into the the 3 main DLLs (ex. main.dll), rather than using common.dll. Since main.test.dll does not test the common code it shows up with 0% coverage. I can't exclude it when running NCover because it isn't a separate assembly.

using

.NET 2.0.50727
NUnit 2.2.8
NAnt 0.85.2006-03-19
NCover 1.5.5.0
NCoverExplorer 1.3.5.1921