Arjay and GCDEF:
The instructions for adding the new class "NewDialog" didn't quite match with my version. I did create a new class (Project -> Class Wizard -> Add Class). I left the base class "CWnd" - should it perhaps be CFrameWnd? Would this make the class/function available? (I guess #include isn't sufficient.)

Paul and GCDEF:
Thank you for that extremely detailed look at structure - it was very helpful. As I said, I have very little background in programming and this is all very new to me so I appreciate the information. I thought DoModal was a system command that would open/create the dialog box I created - so you're saying I haven't made the dialog box available in the public interface? How might I define that?

I hope my questions don't sound too stupid, it's a bit overwhelming to know where to start building a foundation!
Thank you all again for your help!