Excel - Elapsed Time - Calc.

[Rollingthunder]

I know this subject has been touched on here and I have diligently searched and pulled up three related threads. I've messed around with every combination I can think of and failed so far.

I want to calculate elapsed time when the end time is over 24:00

eg.

Time on: 23:00
Time off: 00:30
Elapsed time = 1:30

thanks.