Automatically adding generated source files to an xcode project

I am using an IDL which automatically generates source files for my xcode project. Does anyone know how I can automatically have the generated files added to the project? Currently I have to delete the current files from the project and add the new ones. This gets really annoying.

Using a folder reference works for the header files but xcode doesn't want to recognize any files in a folder reference as source files. Has anyone ever found a solution to this problem?