Find the index of a particular function in a COM Vtable

I am trying to hook up a function SetCooperativeLevel

in a DirectDraw object. Is my goal very similar to the one in this question API Hook to COM Object Function? However, the only problem is that I do not know the exact offset in the IDirectDraw

vtable for SetCooperativeLevel

. Is there a way to get this, perhaps <ddraw.h>

or programmatically?

Here's the interface declaration for IDirectDraw

, however I'm not sure how this corresponds to the vtable.

DECLARE_INTERFACE_( IDirectDraw, IUnknown )
{
    STDMETHOD(QueryInterface) (THIS_ REFIID riid, LPVOID FAR * ppvObj) PURE;
    STDMETHOD_(ULONG,AddRef) (THIS)  PURE;
    STDMETHOD_(ULONG,Release) (THIS) PURE;
    STDMETHOD(Compact)(THIS) PURE;
    STDMETHOD(CreateClipper)(THIS_ DWORD, LPDIRECTDRAWCLIPPER FAR*, IUnknown FAR * ) PURE;
    STDMETHOD(CreatePalette)(THIS_ DWORD, LPPALETTEENTRY, LPDIRECTDRAWPALETTE FAR*, IUnknown FAR * ) PURE;
    STDMETHOD(CreateSurface)(THIS_  LPDDSURFACEDESC, LPDIRECTDRAWSURFACE FAR *, IUnknown FAR *) PURE;
    STDMETHOD(DuplicateSurface)( THIS_ LPDIRECTDRAWSURFACE, LPDIRECTDRAWSURFACE FAR * ) PURE;
    STDMETHOD(EnumDisplayModes)( THIS_ DWORD, LPDDSURFACEDESC, LPVOID, LPDDENUMMODESCALLBACK ) PURE;
    STDMETHOD(EnumSurfaces)(THIS_ DWORD, LPDDSURFACEDESC, LPVOID,LPDDENUMSURFACESCALLBACK ) PURE;
    STDMETHOD(FlipToGDISurface)(THIS) PURE;
    STDMETHOD(GetCaps)( THIS_ LPDDCAPS, LPDDCAPS) PURE;
    STDMETHOD(GetDisplayMode)( THIS_ LPDDSURFACEDESC) PURE;
    STDMETHOD(GetFourCCCodes)(THIS_  LPDWORD, LPDWORD ) PURE;
    STDMETHOD(GetGDISurface)(THIS_ LPDIRECTDRAWSURFACE FAR *) PURE;
    STDMETHOD(GetMonitorFrequency)(THIS_ LPDWORD) PURE;
    STDMETHOD(GetScanLine)(THIS_ LPDWORD) PURE;
    STDMETHOD(GetVerticalBlankStatus)(THIS_ LPBOOL ) PURE;
    STDMETHOD(Initialize)(THIS_ GUID FAR *) PURE;
    STDMETHOD(RestoreDisplayMode)(THIS) PURE;
    STDMETHOD(SetCooperativeLevel)(THIS_ HWND, DWORD) PURE;    // I'm trying to hook this
    STDMETHOD(SetDisplayMode)(THIS_ DWORD, DWORD,DWORD) PURE;
    STDMETHOD(WaitForVerticalBlank)(THIS_ DWORD, HANDLE ) PURE;
};