The simplest thing to do to make 8, 9 and 10 comboboxes so that the grid displays the displaymember and not the valuemember. If you do this, then you can use code like this in a grid.Model.QueryCellInfo event handler to display the tip.
if(e.RowIndex > 0 && e.ColIndex == 2)
{
e.Style.CellTipText = this.grid[e.RowIndex, 8].Formattedtext;
}