STAMFORD - More than 120 teenagers lined the streets of Stamford today, joining a movement to end poverty at home and help the poor in other countries.As part of an event celebrating the 20th anniversary of the youth-based organization Build-On, teenagers spread through the city, stopping passersby and asking them to pledge to do at least one act of community service.Some of the people who were approached by the teens say they want to pitch in."They're really working hard, they've got a lot of energy, and I think they're really going to make a difference," says Maurice Muchene.Build-On is a national after-school program founded in Stamford that's made up mostly of urban teenagers focused on building a better future."If one person wants to do it, there's bound to be more people to help out too," says participant Grace Robalino.Build-On