B should be larger than A, to avoid negative times, which Excel doesn't
represent very well.
One option is to use 0:00 instead of 24:00
Or include dates in the times.

--
Kind regards,

Niek Otten
Microsoft MVP - Excel

"TomS" wrote in message
...

Example of my data

Col A1 = 16:00 (4PM) in time format
Col B1 = 24:00 (midnight)
Col C is formula TEXT(B1-A1,"h:mm") = 8:00 hrs which is correct.

However, when I try to calculate from 24:00 (midnight) to 07:00 (7 AM )I
get
a
#VALUE! error.