OnDragOver and DirectShow window

I'm displaying a DirectShow IVideoWindow on a TPanel inside my control. I'm
using the Videowindow's Put_MessageDrain procedure to point messages to the
TPanel. Only selected windows messages seem to get passed to the owner
control so I can't get the panel's OnDragOver or OnDragDrop to work when the
cursor is over the video window. Any ideas on how I can implement this?.

Thanks,
  Tony