C# Definition:

[ComVisible(false)]
[ComImport, InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("0000000A-0000-0000-C000-000000000046")]
public interface ILockBytes
{
    void ReadAt(long ulOffset, System.IntPtr pv, int cb, out UIntPtr pcbRead);
    void WriteAt(long ulOffset, System.IntPtr pv, int cb, out UIntPtr pcbWritten);
    void Flush();
    void SetSize(long cb);
    void LockRegion(long libOffset, long cb, int dwLockType);
    void UnlockRegion(long libOffset, long cb, int dwLockType);
    void Stat(ref System.Runtime.InteropServices.STATSTG pstatstg, int grfStatFlag);

}

VB Definition:

<ComImport> _
<Guid("0000000A-0000-0000-C000-000000000046")> _
'TODO: Insert <InterfaceType(ComInterfaceType.InterfaceIsIUnknown)> _ if this doesn't derive from IDispatch
Interface ILockBytes
   TODO
End Interface

User-Defined Types:

None.

Notes:

// read a chunk from the ILockBytes object
public int ReadAt(long offset, byte[] buffer, int bufferSize)
{
    IntPtr pv = Marshal.AllocHGlobal(bufferSize);
    UIntPtr pcbRead;

    ((ILockBytes)comPtr).ReadAt(offset, pv, bufferSize, out pcbRead);

    int length = (int)pcbRead.ToUInt32();
    Marshal.Copy(pv, buffer, 0, length);

    Marshal.FreeHGlobal(pv);
    return length;
}