My Popularity for week

I am using my popularity plugin in my blog http://studycycle.org to show “top 20 popularity”. But, posts in the list are the most popular posts for whole time.
I need to show “top 20 popularity” (for whole time as it is), “top 20 popularity for this week”, “top 20 popularity for this month”.

http://wordpress.org/extend/plugins/my-popularity/