Rank a Summarized Running Total?

[DeviousDi]

Hi,

I need to rank a summarized running total, similar to how excel would use the 'rank' function.

Here's my table, briefly:

Area Volume of Invoices Value
D44 8 6592
D02 12 75182
20 81774

The total column for the volume of invoice is a summarized field, this being the formula

if {invoices.amount_open} <> 0 and {@Query_Type} = 'Q'
then true
else false

My data is group by area, and I don't want to change the way it is sorted. I just want to add an extra column to the end that will add a number (this being the ranked number).

Is it possible?

I've looked through the posts on here, but can't find anything for ranking a summarized field.

Thanks in advance.