Get 2 cells with date and time to show difference in HH:MM:SS

Dear All,
Wonder if someone can quickly help me with attached.

Need cell C3 (hh:mm:ss) to show the difference between B3 and B1 (both mm/dd/yy hh:mm:ss) When I have B3 as the next day cell C3 does not display the correct value.

Must be something simple.....I just cant seem to figure it


Thanks to any that can help me out.

Just change the display format. You set it to HH:MM:SS which will keep it constrained to 24 hours. In the custom formats choose this format [h]:mm:ss and it will be a total hour difference not the rollover effect you are getting now.

Please see attached example.

If I use a blank document then the suggestion above works just fine. However, if I do the same ( [h]:mm:ss )on the attached doc then I get #VALUE! What is the difference between a blank doc and mine?

Can anyone help solve this as I can't see why it works in one doc and not another