[c#]
public void InvalidateCell(FlyGridViewPort port, NodeBase node, Column col)
{
  int colIndex = Array.IndexOf(port.Columns.VisibleColumns, col);
  if (colIndex != -1)//column is visible
  {
    int rowIndex = port.Rows.GetRowFromNode(node);
    if (rowIndex != -1)//node is visible
    {
       Rectangle r = port.GetRectangle(port.Bounds, colIndex, rowIndex);
       port.FlyGrid.Invalidate(r);
    }
  }
}