2 methods come to mind:
1) add the date and date + 6 to the formula (since it really won't change the outcome)
2) add another level below the current one based on date and display there (suppress the current header)
adding the date should be something like:
(DatePart("ww",{BAQReportResult.LaborHed.PayrollDate},crMonday) + " - " + totext({BAQReportResult.LaborHed.PayrollDate}, "MM/dd/yyyy") + " - " + totext(dateAdd("d", 6, {BAQReportResult.LaborHed.PayrollDate}), "MM/dd/yyyy")
HTH