Insider buying and selling for stock?

One of the small cap value stocks i'm looking into has lots of insider buying/selling on 4/21/11. Exec VP of company bought shares, Senior VP bought a lot more than he sold that day, the chief accounting officer also bought more than he sold, and the president just bought. But what does it mean when they buy more shares then they sell? If they buy so many shares why do they also sell a few on the same day? Is this a good outlook for stock or not or hard to tell?