Sum will compute the total you want if you have a relationship that uses that date range to match to the records for which you want such a sum.
If you have
TableA::DateStart < TableToSum::Date AND
TableA::DateEnd > TableToSum::Date
Then a calculation defined in TableA as:
Sum ( TableToSum::NumberField )
will compute a total over the date range from DateStart to DateEnd.
Summary fields can also compute a total over a date range, either using the same relationship above or as a found set or sorted group of records in a summary report where that found set or group represents your date range.
And ExecuteSQL could be set up to compute a total from a date range.