def _to_range(col, row):
    """returns an Excel range string, e.g. 0, 0 => A1"""
    cell = ""
    while col >= 26:
        cell = "%s%s" % (chr(ord("A") + (col % 26)), cell)
        col = (col // 26) - 1
    cell = "%s%s" % (chr(ord("A") + (col % 26)), cell) 
    cell += "%d" % (row + 1)
    return cell