Request blockchain for transactions
Not sure what exactly you need to do once you have found your information as that can be a big drive in what tool you use as well. However you can use bitcoind api which is packaged with bitcoin-qt to get all infromation about a transaction using this command.

gettransaction &lt;txid&gt;


It will return to you all the infromation about that transaction, I would use some other tool build on top of it such as a php api or whatever your favorite language is. Here is one that I made to interact with it via PHP https://github.com/michaeljs1990/Bitcoin-PHP-API .

More about the bitcoind API can be found at https://en.bitcoin.it/wiki/Original_Bitcoin_client/API_Calls_list