throw exceptions to com

Question

Hi !
Beeing a long time vb6 com developer I am now getting heavy into c#. We are building a module for an external COM application, and we need to be able to throw errors to this com application. In vb6 we used -err.raise num, description- from our module and this was then caught by the application for further processing. So what I need is a way to send an exception to the com application from our c# module in the same way we use err.raise in vb6. Thanks for all help.