MFC multiple document types

Are you using the document/view architecture? If you are, this makes life a lot easier. If you're using the document/view architecture with MDI, then you're already using one document type. Look in the overidden InitInstance method of your application class. You should find some code which creates a new CMultiDocTemplate, initializes it with it's constructor, then calls AddDocTemplate to complete the job. To add new document types, just repeat this process. I'd highly recommend that you get Jeff Prosise's "Programming Windows with MFC, Second Edition" if you want to learn more about this topic, and pretty much anything else to with MFC. Below is some example code illustrating what I said above:

// App-wizard code...CMultiDocTemplate *pDocTemplate;pDocTemplate = new CMultiDocTemplate(	IDR_MAINFRAME,	RUNTIME_CLASS(CBlackDoc),	RUNTIME_CLASS(CChildFrame),    // custom MDI child frame	RUNTIME_CLASS(CBlackView));AddDocTemplate(pDocTemplate);// My new document type...pDocTemplate = new CMultiDocTemplate(	IDR_MAINFRAME,	RUNTIME_CLASS(CWhiteDoc),	RUNTIME_CLASS(CChildFrame),	RUNTIME_CLASS(CWhiteView));AddDocTemplate(pDocTemplate);