Apache last modifed header question with mod_headers

how do I set this in my .htaccess file?

[jeremy goodrich]

I've been looking through my logs, and for fun, I'd like to let the spiders know the content is new, and was only published, say, 2 minutes before the spider got there. :) And I'd like to let caching servers know they shouldn't hold my stuff, so that I can get a better read on traffic. This should increase the bandwidth I'm using, but be much more fun to read in the log files.

I've read through some of the apache mod_headers documentation at apache.org, but I'm still a little confused. I tried a couple things, and they gave me a 500 error after I tried accessing the site with the new .htaccess file in place.

Does anyone here have some experience playing with mod_headers? I think the command in the file should be
ExpiresActive On

after that, though, what I found was a little hard to follow. still not very technical ;)

[bobriggs]

I tried this once too jg.

Then I went to my shell account, typed in:

httpd -l

at the prompt to get a look at the extension modules which had been compiled in on my server. No mod_expires.c loaded on my server. You probably want to check this first...

[netcommr]

jeremy, if you don't want cacheing, look into e-tag headers. for modified dates, look into using tar to actually change the date, there is a trick...