Thunderbird USNET download problem

I'm trying to subscribe to a USENET newsgroup using Thunderbird.

When I set-up the subscription and begin to download the posted headers it tells me there are over 400,000 (going back to 2003). :eek

I've been all over the tool bar menus searching for some way to tell Thunderbird that I'm only interested in downloading (reading) the most recent 500.

Can't find a way to tell Thunderbird to stop reading all those 399,500 from yesteryear and just give me the recent ones.

All I found was an option to tell it not to SAVE any past xx days old.

Help! I need to turn off the fire hose.