How to write to Visual Studio error window from Custom Tool without using IVsGeneratorProgress.GeneratorError

I am writing a custom tool extending the IVsSingleFileGenerator interface of Visual Studio. Through IVsGeneratorProgress.GeneratorError I can output simple warning/error information, but I need more control over what's output. Specifically, GeneratorError alwa开发者_如何学Pythonys outputs the source file triggering the single file generator as the file in error, but the tool processes multiple artifacts, and I need to be able to output errors for those.