They cannot disclose it publicly(number of shares) but it is part of 10b-5 trading plan, has to be done at a B/D and there are restrictions on when the trades are entered. even the owners dont know when the trades will be executed but they know how much they are approved to trade and get notice of executions after the fact. Then they report on form-4 monthly the previous month.
News 
Market Data 
Discover 
