Need advice - VC6 to VC7 migration

I have a VC++ 6.0 app that I would like to upgrade to .NET. We want to keep the desktop app as it is, but also add a web interface. I have a new .NET data grid control that I would like to add to the application for use from both the desktop and web interfaces.

I am planning on making all code that I'd like available from the web interface managed, but I don't know what to do with the existing dialog boxes. How can I make them work with my new .NET data grid control? Do I need to change all my dialogs to start using the Windows Forms class? If so, does anyone have examples of how to do this?