calculate change of totals on list page

Hello,

I have a list page with the following fields:

AccountName, PreviousYear, LastYear, AnnualIncrease.

Annual Increase is calculated in my SQL query using the "previous year" and "last year" amounts, per account. On the designer page, I have totals set for previous year and last year, so my page looks like this:

I need to take the Total from the bottom of the "Last Year" column and the Total from the "Previous Year" column and calculate percent change of these 2 numbers and display this at the bottom of the Annual Increase column. I assume I'll use Javascript onload event and get the totals from those 2 controls (which, on the designer page, I've given an item ID of totals_prev_year and totals_last_year), and then calculate the percent change, but then how do I display that result at the bottom of the Annual Increase column? Or maybe there's another way to do this..?

Thanks,
Tim