I have a bunch of data that came from stopwatch readings. Most of it
is under 10 minutes, but occasionally I will have a value as large as
several hours.

Is there a way in Excel, without writing a macro, to display time data
as a number using the largest units (hours, minutes, seconds) having a
value >= 1?

Some examples:

 Reading        Display
 00:00:12.34    12.34 sec
 00:00:59.99    59.99 sec
 00:01:00.00     1.00 min
 00:01:30.00     1.50 min
 00:59:30.00    59.50 min
 00:59:59.50    59.99 min
 00:59:59.69    59.99 min
 00:59:59.70     1.00 hrs  /* this one is tricky */
 01:00:00.00     1.00 hrs  
 12:34:56.78    12.58 hrs

and so on...

Assume the reading never exceeds 23:23:59.99.

I have written a macro in another language to accomplish this, so I
could port it over to VBA, but if there is a way using custom formats,
I would prefer that.