Public Function Subtract( _
    ByVal Unit As String, _
    ByVal Value As Double _
) As 

public IAgDate Subtract(
    string Unit,
    double Value
);

public: IAgDate^ Subtract(
    String __gc ^ Unit,
    double Value
);

public IAgDate subtract(
    String Unit,
    double Value
);

public: HRESULT Subtract(
    BSTR Unit,
    double Value,
    IAgDate ** ppDate
);