OK, I hope I'm repeating what you already know (or else I will be worrying about my "children").
Major institutions used to give broker "not held" orders to "work"...so that they would get a "fair" price on their 250,000 share order (sort of). This has changed recently where the institutions tell the broker that I will buy (sell) 250,000 at the VWAP (as determined at end of day). This can cause some grief for brokers who are too slow to recognize a straight up market, since they will have to pay more than the VWAP to provide the stock to the customer. We teach our traders to simply watch for "size" trades at or near the current VWAP, and perhap ride the market up for a while, until the broker may actually sell a small portion of the stock to keep the VWAP in line with their average price.
If this is new information, then please think about it....if it's not, try to put yourself in the shoes of the broker on the floor. This has been extremely valuable to those who understand it, and extremely costly for those who try to "chart it" as a significant number.
Just trying to help....
Don