Call this function after you have made any modifications to the document.
virtual void SetModifiedFlag( BOOL bModified = TRUE );
Flag indicating whether the document has been modified.
By calling this function consistently, you ensure that the framework prompts the user to save changes before closing a document. Typically you should use the default value of TRUE for the bModified parameter. To mark a document as clean (unmodified), call this function with a value of FALSE.