1) Perform a find with criteria like this: 12/1/2011...12/31/2011 to find dates in a date range. This can be done in a script if you use steps like this:
Enter Find Mode 
Set Field [YourTable::DateField ; Table::GlobalDate1 & "..." & Table::GlobalDate2 ]
Perform Find 
2) A summary field can compute the total of all records in the found set produced by 1)
3) and what calculations would those be?