I am performing validation on missing data when loading the grid and applying a red border to a cell where the data is missing so the user can identify missing data quickly. I have my grid groupable = true so the user can group by column headers. My problem is I lose the cell border after the user drag/drops the column header into the "Drag a column header and drop it here to group by that column" area. Any ideas on what fires after the grouping is done or where I can insert a custom method to reapply my cell border.