Usenet posting disable?

Is there a way to disable users to post messages on the Usenet (news), but enable them to read messages?
My ISP is very strict about non solicted messages so when someone posts a msg on the wrong group, my internet account gets a 2 week ban.

Thank you very much,
Dakky

I think that uses the same port to post vs read.

So.. thats going to make it difficult. protocol 7 filtering may do this, however, gets more complicated.. hmmmmmm… any other thoughs?

just make a burst rule, reading will be fast, but uploading/downloading will be very slow.
http://www.mikrotik.com/testdocs/ros/2.9/root/queue_content.php#6.54.4.2