Final update Sorry, I'm not able to figure out what's wrong with this, and since Frank has a better solution for Visual Studio integration, I'm cancelling this attempt. If you're interested in the source code, send me an email! I think it's better if I focus my efforts on the MSBuild script instead....
As you may have seen in previous posts from me, I've created a MSBuild script that makes it easier to create Sandcastle documentation files. But hey, why stop there? Wouldn't it be nice if the whole process was integrated in Visual Studio like all other products? Well, I couldn't help myself, so I tried...