RE: 200@.39 500@.50Oscar: You can not sell below the ask. Either the market or your broker will not let you do something stupid like that (unless your broker is braindead or you deal in odd lots) If you see the last trade is below current ask, that just means that the spread has moved up. Obviously a bid is now available that was not before.
RIGDIG: I have had open limit orders (as opposed to "all-or-none") that will be filled as shares become available (at my ask price). If I get 1000 shares in 5 different 200-share trades throughout the trading day, I will only pay one commission.
Woody.