module RubyXL::WorkbookConvenienceMethods

def modify_alignment(style_index, &block)
  old_xf = cell_xfs[style_index || 0]
  new_xf = old_xf.dup
  if old_xf.alignment then
    new_xf.alignment = old_xf.alignment.dup
  else
    new_xf.alignment = RubyXL::Alignment.new
  end
  yield(new_xf.alignment)
  new_xf.apply_alignment = true
  register_new_xf(new_xf)
end