I think your question has an underlying misconception. The wallet only contains bitcoins in an abstract sense: In realitas the wallet only stores the private keys that enable you to spend the bitcoin balance that is associated with your addresses. Think of it this way: When you look into your wallet, you only see a number of little boxes. You know that all these boxes are yours, but from the outside all boxes look the same, regardless of what they contain. You can only know how much you have in this boxes, by opening each of the and counting their contents. This "looking into the boxes" step happens by looking up the balances of your addresses in the public ledger (the block chain). The wallet.dat might contain the balance that was last counted when you compared to the blockchain, but can only be updated to the current state when counting the contents of the little boxes again.
So, without downloading the blockchain and having your software calculate your current balance, you could only check "if everything is alright" by looking up specific addresses. If you received your bitcoins in one transaction the balance is associated only with one address and this address could easily be written down or memorized separately from the wallet. You could then proceed to look up the balance of it on a website such as for example http://blockchain.info. This can be done safely, as the address alone does not allow anyone to spend the bitcoins.
So, summing up: Just from the wallet.dat you cannot get an update on the balance without acquiring additional information. You can however check the balance of addresses directly by using publicly available information.
2Can I get these addresses given a
wallet.datfile? – Hudon – 2013-08-25T02:55:52.550I think yes, unless it is encrypted and you don't know the passphrase. – Murch – 2013-08-25T04:08:43.173
1I've reworded the question to correct the "wallet doesn't contain the bitcoins" error. The question remains unanswered though: how do I figure out my balance given just the wallet.dat file (no blockchain)? – Hudon – 2013-08-25T14:05:55.333
The blockchain is needed, since your coins are in blockchain, not in a wallet. You can use already mentioned website blockchain.info to check balance of your address, without messing with blockchain at your side. – ripazha – 2013-08-25T15:09:49.053
I updated my answer to reflect his updated question just before your comment. :) – Murch – 2013-08-25T15:39:03.357
3There seems to be a contradiction. First you said that it is possible to get the addresses given a
wallet.datfile, but then you updated your answer to say that the only way to get these addresses is to write them down a priori. Knowing which one is true would be useful so we can get a final answer to whether or not the original problem can be solved. – Hudon – 2013-08-25T18:32:19.383My impression was that you didn't want to hook up your wallet after receiving the money to keep it safe. Well, before not accessing your wallet, you'd have to get the address from your wallet that is associated with the balance you want to check on later and then look up that address whenever you feel like it. If you don't mind to access your wallet later, then you could get the addresses later. However, by itself the wallet can't tell you the balances associated with your keys, much like your car key can't tell you if your car is still parked in the road while you are inside. – Murch – 2013-08-26T01:31:10.923