Jerry, I'll share my experience from a past dividend distribution...
I had an open buy order on an issue I held to increase the # of dividend shares I would receive for about a week. I had to chase the ask and it finally filled on the date of distribution. Although it took 2 or 3 days to settle the order I got the divedends due... the issue actually popped up after the dividend date :)
Some say you should get your order filled the day before the dividend date to be safe but I understand you get credit as the holder of record @ the close of the day. Obviously they would not distribute a double divie to 2 people that owned the same share for part of a day nor skip a divie due to a share that was changing hands on the dividend date.
Good luck Jerry and I hope everyones open MEDT orders fill in time!