Locking for new subjects but not replies! HELP

Hi I'd like to lock a forum. I'd like to lock it only for creating new topics/subjects but not for replying . Example: I have a topic called , "what food do you like", I lock the forum and there is still the topic : "what food do you like", however people cant make new subjects because it is locked, but they can reply to them. How do i do that. When I lock a forum it locks both rpelies and new subjects. Help please for this is urgent.

Timothy

Regarding that particular forum:
In your forum permissions untick OPEN A TOPIC for members, they will still be able to reply but not start new topics.