I want to do a sort on a column containing values such as:

Feb
- 84
- 2
100
- 40
20
- 13
-350

I want to sort this based on the largest change,
regardless of whether it's positive or negative. In other
words, I want it to come out as:

Feb
-350
100
- 84
- 40
20
- 13
- 2

I know I could do this by selecting the absolute value
into a hidden column and actually doing the sort on the
hidden column. But, I've got 13 columns (each month plus
a total), and I really don't want to add all those hidden
columns.

Anyone know how to do this with a custom sort?