Odds of 3 people with pocket pairs all flopping a set in holdem

I have no clue how to calculate this and someone asked me. I assume the odds are different if you count the odds of 3 people having pocket pairs dealt and then all 3 flopping sets, compared to WHEN 3 people have pocket pairs how often do they flop the set. Or maybe not...its 2:45am [img]/images/graemlins/laugh.gif[/img]