How do I access a texture in DirectX 9c?

I've been researching how to get access to the texture inside a native plugin (http://docs.unity3d.com/Documentation/Manual/NativePluginInterface.html). I've read, and implemented the sample project shown on that page.

I also found the Texture.GetNativeTextureID method (http://docs.unity3d.com/Documentation/ScriptReference/Texture.GetNativeTextureID.html). However this only works for OpenGL\ES.

Now that I have a pointer to an IDirect3DDevice9, I'd like to use its GetTexture method (I am not sure this is the right way to do this).

However, I can't do this without access to the stage (index?). How can I access a texture in DirectX 9c as a plugin for Unity3D?

 

Bump -- still no idea how to do this. Any suggestions?

 

Bump -- does Unity3D support this? OpenGL won't work for us, so we must use DirectX to access the texture data.