Official Arduino ethernetshield and the W5100 buffer

Hello,

I am using the Arduino 1.0 Ethernetlibrary. I am using a EthernetServer and EthernetClient. Is it possible to write to the W5100 buffer using EthernetClient.write w/o transmitting the data until a certain byte count is reached? Or could I do this using sockets?

Thanks,

-ren