Custom Formatting: Can I set up a condition?

[Phrank]

Here's what I have:

Column A = Start time
Column B = Nominal Sample Time (i.e., 5 m, or 5 min from start time)
Column C = Relative Sample Time (Actual time - start time)
Column D = Actual Sample Time

Wanted: If(time in column C is less than 60 minutes, I need format to
be ‘x m’ where x = # of minutes)

If(Itime in column C is greater than 60 minutes, I need
format to be ‘y h x m’ where y = # hours and x = # minutes

BUT, I don’t want any 0 hours or 0 minutes (e.g., 0 h 4 m
must = 4 m. Or 5 h 0 m must = just 5 h)

I've tried the custom formatting of (h "h" m "m"), which works for the
whole thing (e.g., 5 h 42 m), but it also yields 0 h 4 m and 5 h 0 m.
I need the later two to be just '4 m' and '5 h'.

I also need it to show 24 h (and greater if there has been more than
24 hours passed).

Finally, the Actual Sample Time may be before the Start time, which
may result in a negative time. How can I get it to display a negative
time.

Thanks for any help, and please let me know if you need some
clarification to help me.

Frank