Count weekly occurences of a value within a time period

Hi all,

I am new to this forum and fairly new to Excel so apologies if this is a simple question.

I want to take my large spreadsheet of data in this format:

Promotion\ Start \ End \ Group
Promo 1 2011-11-01 2011-11-22 A
Promo 2 2011-11-22 2011-12-06 A
Promo 3 2011-12-06 2012-01-03 B
Promo 4 2012-01-03 2012-01-24 C
Promo 5 2012-01-24 2012-02-14 C
Promo 6 2012-03-06 2012-04-03 D
Promo 7 2012-04-07 2012-05-22 E
Promo 8 2012-05-22 2012-06-19 E
Promo 9 2012-06-19 2012-07-24 A
Promo 10 2012-07-24 2012-08-14 A

and reformat it like this using formulas:

Week Commencing \ Group A \ Group B \ Group C \ Group D \ Group E
2011-10-31 6 0 0 0 0
2011-11-07 7 0 0 0 0
2011-11-14 7 0 0 0 0
...

and so on. Such that the values in the table denote how often Group A-E occurs in each week. (For example, Promo 1 occurs from 2011/11/01 - 2011/11/22. Therefore a Promo 1 occurs 6 times in the week commencing 2011/10/31 (6 out of 7 days), 7 times in the week commencing 2011/11/07 (every day of the week), and so on.. as Promo 1 is in Group A, the values are inputted in the Group A column)

Thank you in advance for your help!

Edit: Managed to use this formula but it only works for one promotion at a time. Shown in attached document