How to limit duration to a given time range

How are you accounting for cases that span multiple days (assuming that is possible)?

If you have a date/time value you can use the DATEDIFF function to calculate hours between date times. E.g.

DATEDIFF([Start Date/Time],[End Date/Time],HOUR)

If you have Date and Time as seperate columns you can add them together like so:

DATEDIFF([Start Date]+[Start Time],[End Date]+[End Time],HOUR)

If you only care about comparing time and not date (if case open/close are always the same date) you could use an arbitrary date e.g.

DATEDIFF(DATE(2024,01,01)+[Start Time],DATE(2024,01,01)+[End Time],HOUR)

UPDATE: apologies, I completely missed the part where you said you needed to calculate work hours. Greg's solution looks more promising for that.