Nasty LPDIRECDRAW -> LPDIRECTDRAW7 conversion

I've been studying the DDrawXCL DirectShow example but i've hit a stumbling block converting what i've learned into my app. I use LPDIRECTDRAW7 (and am not about to change it all now) but after way too much work on this, i've discovered that the IDDrawExclModeVideo method, SetDDrawObject, wants LPDIRECTDRAW. Syntax:

Code:

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HRESULT SetDDrawObject(
    LPDIRECTDRAW *pDDrawObject
);

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Anyone know what can be done about this? I'm rather unfamiliar with these interfaces and theres very little in the way of enlightenment coming from the SDK.