Limit maximum number of open threads per user, per forum

[TalkPhotography]

We'd like to be able to restrict members to x number of open threads in a particular forum.

Despite my usually good google-wu, I can't find anything that may do this.
In this particular subforum, members have the ability to close their own threads, but we'd like to restrict the maximum number of open threads per user in this forum to x (So theyre forced to close old threads if they want to open a new one).

Is there anything that can do this?

Thanks in advance