varkind

tobj = WIN32OLE_TYPE.new('Microsoft Excel 9.0 Object Library', 'XlSheetType')
variables = tobj.variables
variables.each do |variable|
  puts "#{variable.name} #{variable.varkind}"
end

The result of above script is following:
   xlChart 2
   xlDialogSheet 2
   xlExcel4IntlMacroSheet 2
   xlExcel4MacroSheet 2
   xlWorksheet 2