[Boost-users] betweenness centrality

Hi, i'm an italian developper and i have a question about the function brandes_betweenness_centrality. I would know if it's possbile to run brandes_betweenness_centrality only on a subset of nodes of a graph, because the execution of the function on the entire graph is too long. I want to calculate the betweenness approximation starting from the value computed for this subset of vetexes. Sorry for my english(i'm italian...).