This could give the right tool:

First create a new column that identifies what dates are Summer/Winter.
Then make a Pivottable:
Row: Date, W/S, Customer
Col: Staff
Data: Staff

Done

Ola Sandstrom


Screen dump:

Count of STAFF.........................STAFF
DATE.............W/S...CUSTOMER..........Staff A......Staff B.....Staff
C......Grand Total
12/15/2005...W......Customer
A..........2...................................... .......2
......................W.......Customer
C........................................1........ ......1
12/15/2005..Total...............................2.......
......................1..............3
12/16/2005..W.......Customer
A..........1...................................... .......1
.....................W........Customer
B.........................1....................... ......1
12/16/2005 Total.................................1...........
..1..............................2
12/17/2005..W........Customer
A..........2............................1......... .....3
12/17/2005..Total................................2......
.......................1..............3
Grand Total.........................................5...
...........1..............2..............8