DataGridView.CellFormatting Doesn't Work When Grid Is Sorting

I have a datagridview control that where I need to color the rows based on a value in one of the cells in each row. I'm using the CellFormatting event like so: [code]This works fine when the grid loads and when I scroll it, etc. But when I click on the column headers to sort the grid, e.Row Index is always zero and all of the rows get the formatting of the first row..[code]For some reason, e.RowIndex is set correctly here but not on the other methods. The only thing you have to worry about here is it can be -1. But when I tried to use other methods, including PrePaint, I had to deal with it always coming up zero on a sort. If I exclude the zero case, like I excluded the negative one case about, then the first row is always white!!! I'm not sure why this works, but it does. It also produces no flicker beyond what I got using the CellFormatting event.