How do I accomplish Variable date controlled summation of data

[Capt Samm]

I am making an attendance sheet for school in which there is a sheet for each grade and a summary sheet on which I wish to show the total number of the Absents (A), Late (L) and Late excused (LE) for each student, for each marking period.

Each grade has a sheet that has dates across the top of the table and names down the sides thus:

Name 8/15 8/16 8/17 8/18 8/19 8/20
a
s
d
f
g

Simple enough, I can do that, manually. However, the dates of the marking periods are on the summary sheet as:

Marking Periods
Start 8/15/10
End 1 11/1/10
End 2 1/1/11
End 3 6/20/11

How can I reference the dates on the summary sheets so that the proper time period is accessed by a countif = "L" function ie, it counts all the "L" entries between 8/15/10 and 11/1/10?

Each year the marking periods change of course and instead of changing all of the sheets for each grade to reflect those changes, I would rather have a grid that encompasses all the possible (reasonable) dates and delineate the periods as shown.

Any help would certainly be appreciated
Regards,

Capt Samm

Rules are made to be expanded by creativity not adhered to slavishly.