Finally I think I have got it and have committed changes to TimeTextCtrl so
that NTSC drop-frames works correctly for both dragging and inc/dec of the
frames, secs etc.. If anybody out there who has NTSC drop-frames
experience I would appreciate a test - for example one minute down from
00:10:00;01 (or is that 00;10;00;01?) is conventionally 00:08:59;29 or
Will try and remember to update the comments in th file shortly.