how can i set a post limit on specific forum ( phpbb )

hello

i have a phpbb board and i have mainly 2 forums.one of them is so important for me and the other is not.but users like to post messages to the second one.then the post number of the second forum (which i dont want) increases so much. i want to set a post limit daily.

for example the 2nd forum has a limit 100 messages per a day.but the other is not.

how can i do his?

thanks