if you want to calc hours you need to DATE & TIME.
1/1/2020 8am & 1/1/2020 5pm ,
then use DateDiff("h",startDate, endDate)
using time alone wont work If you cross midnight.
The above works it both fields are on the same record.
if you have separate recs:
person, DateStamp
bob ,1/1/2020 8am,
bob, 1/1/2020 5pm ,
you must use vb to cycle thru the records, to calculate elapsed time.
i run a report by dumping my data range into a 'report' table, scan while writing the elapsed using the previous timestamp:
person, DateStamp, elapsed, units
bob ,1/1/2020 8am, 0
bob, 1/1/2020 5pm, 9, hrs