Sort subforums by last post?

[sportfreund]

Hi everyone!

We are searching for a solution for the following problem:

The subforums should be sorted by the date of the last post:

sub 2 - day 1
sub 4 - day 2
sub 3 - day 3
sub 1 - day 4

For example a few days later:

sub 3 - day 1
sub 2 - day 2
sub 1 - day 3
sub 4 - day 4

etc.

Is there any possible solution for vbulletin? Add-on, template editing...?