Column calculations in Crystal crosstabs

Can anyone help with how to calculate a percentage variance on 2 columns of a cross tab. The number of columns in crosstab can vary from 2 to many more. The percentage variance needs to be calculated as:

if first column then "colunm data" else
((this column - previous column)/Previous column )*100

How do I reference the columns in a crosstab?Just a *Bump* of sorts, I suppose.

I'm looking for a similar solution, though I'm not looking for a percentage variance. I'm referencing dollar amounts by category, broken out over two calendar years.... so far so good in the cross-tab. Totalling the fields is of no value, so I've suppressed the totals columns/rows. What I do need to be able to do is to subtract the 2007 data from the 2006 data to come up with the raw difference. For example, in the attached screen shot, I need to subtract the 2006 data from the 2007 data moving across.

How can I create a formula to accomplish this?

Any assistance from the experts is greatly appreciated. One of these days I'll get to take my swim fins off....