Sort whilst keeping the rows in sub order.

Hi Guys
Sort whilst keeping the rows in sub order.
I have a set of numbers which have the same column headings but are in different row groups. The row groups have percentages applicable Column F to each row and these are added up to give a total Column I. What I am looking for is to sort out the total for the groups using column I into descending order but keeping all the rows in each group in their original order.
I am sorry the title is so obscure. I have no idea how to make it short and simple. I have up loaded a file which makes it more straight forward. I have no idea how to start this.

Again thanks in advance.

Mark