No, they're not similar at all. Vienna is a basemalt, and caravienna is crystal malt made from Vienna malt. You'd be closer to use a crystal malt like crystal 20L.
Caravienne is no made from Veinna base malt. It is a trade name for a crystal malt that is 20 to 24 lovibond. If you can't fine it you can use crystal 20 or 30. It won't be exactly the same but it will be close.