Crosstab YTD averages problem

Question

Pulling a large set of customer contacts (100,000s of rows) with each row being a contact. I have a crosstab which groups by location and employee, when the detail rows are the types of contacts (in person, telephone, etc) and then I have months across the top. Here's the problem I'm having:
I need to calculate the average # of contacts per business day. I could countdistinct(contact_date) if I were basing the average on the number of days on which contacts occured (for each dept), but the report has to calculate averages for all departments based on the same # of business days per month (21 in January, 19 in February, etc.). If I just put the number of days on each row in the dataset, I could do min or max or avg and it would work fine for the months' averages, but the totals at the end for YTD won't work. I can't sum, because I have the # of business days on each row, so 1000 contacts in a month with 21 days would put a denominator of 21000.
This is how it would look working the way I want it to.

Answer 1

Thank Graham,
when i use the same technique of setting up a nested counter and highlighting the fields based on that value...
The counter should be set on every column of the row?
It is because i found there is the problem, when i set the counter on every column...all the row will be highlighted without condition (x<=5), i think the counter may overcounted or not work.
for example..
user   action count
1. a     10
2. b     9
3. c     8
4. d     7
5. e     6
when i set the counter (let's say x<=2), on both user and action
i will see the user 1,2 had been highlight and whole action column as well.
and i also struggling with the filtering..
i saw the whitepaper, can it apply in the crosstab?