How do I intercept/ override the file saving mechanism in a doc/view architecture app?

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MFC

I have this sdi app that works like an mdi in that it handles severak documents.

I need to take control of the file saving mechanism.
Since it is mdi-like in nature, when the user clicks SAVE I need to be able to tell the framework whether to lunch the SAVE dialigue box( just as if the user clicked SAVE AS because the document in question has not been saved previously) or not.Also I must be the one to pass the name/path of the file it should save in the event that the file has been previously saved.


Please what do I override? How do I do the overriding?