Custom Formula To Count DOW

I have a set of data being output by a reporting application as XLS data. For each day of business the report is run, I have a set of 100 rows of data. In each of the these rows of data there is a date field and a locationID field.

What I need to do is add a calculated value on each row that specifies the day of the week (MON, TUES, WED, Etc.) and which occurrence of that days of the week it is for the data set. The enumeration of which occurrence of the day of the week (ie. MON-1, MON-1, MON-3) is determined not by how many dates fall on Monday for the data set, but how many Mondays fall between the earliest and latest dates for that location in the data set.

Example:
The data set contains sales data for location XX from 4/6/09 (A Monday) to 4/22/09 (A Wednesday).

The data set contains sales data for location YY from 1/18/10 (A Monday) to 2/9/10 (A Tuesday).

Example:
Location XX's data's earliest date is 4/6/09, it's latest date is 4/22/09
From 4/6/09 to 4/22/09 there occurs:
3 Mondays
3 Tuesdays
3 Wednesday
2 Thursdays
2 Fridays
2 Saturdays
2 Sundays

Location YY's data's earliest date is 1/18/10 it's latest date is 2/9/10
From 1/18/10 to 2/9/10 there occurs:
4 Mondays
4 Tuesdays
3 Wednesday
3 Thursdays
3 Fridays
3 Saturdays
3 Sundays

For all data for location XX, I need to set the new calculated columns to:
Where Date = 4/6/09 & Location = XX, DOW# column = MON-1
Where Date = 4/13/09 & Location = XX, DOW# column = MON-2
Where Date = 4/20/09 & Location = XX, DOW# column = MON-3
Repeat for all dates between min-max date for that location

For all data for location YY, I need to set the new calculated columns to:
Where Date = 1/18/10 & Location = XX, DOW# column = MON-1
Where Date = 1/21/10 & Location = XX, DOW# column = THU-1
Where Date = 1/25/10 & Location = XX, DOW# column = MON-2
Where Date = 1/24/10 & Location = XX, DOW# column = THU-2
Where Date = 2/1/10 & Location = XX, DOW# column = MON-3
Where Date = 2/4/10 & Location = XX, DOW# column = THU-3
Where Date = 2/8/10 & Location = XX, DOW# column = MON-3

Repeat for all dates between min-max date for that location.

A typical data run will have data for 4 or more locations spanning 30-60 days, so figuring out a formula that I can drop onto a column of the exported data so i can run pivot table analysis would be great.