class RubyXL::ColumnRanges

def get_range(col_index)

or split existing column range into multiples.
Locate an existing column range, make a new one if not found, 
def get_range(col_index)
  col_num = col_index + 1
  old_range = self.find(col_index)
  if old_range.nil? then
    new_range = RubyXL::ColumnRange.new(:min => col_num, :max => col_num)
    self.column_ranges << new_range
    return new_range
  elsif old_range.min == col_num &&
          old_range.max == col_num then # Single column range, OK to change in place

    return old_range
  else
    raise "Range splitting not implemented yet"
  end
end