Prune by thread start date

[Morrus]

I'd like to create a link to popular threads this week as an easy way for new folks to dive in.

The following URL works fine:

forumdisplay.php?500-All-Discussion&s=&pp=200&daysprune=7&sort=replycount&p refixid=&order=desc

Except that the prune element includes threads posted to in the last week, rather than started in the last week. I don't want months old threads appearing in the output.

Is there a URL element I can use instead of daysprune=7 which prints by thread start date rather than last post date?