Numbers formulas help

[silvetti]

Hi!

I am trying to work with a table I have.
http://imgur.com/a/JyHXU

What I wanted was for the total to basically check that row and subtract the smaller number from the bigger one this way giving me a total usage.
How can I do that in Numbers ?

Cheers!

 

[I'm a ROb]

Perhaps something like would do the trick:

Total Usage = MAX(B2:B20) - MIN(B2:B20)