OleCreateEmbeddingHelper

[DllImport("ole32.dll", SetLastError = true)]
public static extern int OleCreateEmbeddingHelper(
   ref Guid rclsid,
   IUnknown pUnkOuter,
   uint dwClsCtx,
   IntPtr pCF,
   out IOleEmbeddingHelper ppOEH
);

Microsoft documentation: Link