If you trust blockchain.info the confirmations of the second payment should not matter. We will keep broadcasting the second transaction until it confirms, so although it may take a while it will always confirm eventually.
Otherwise you could manually check the confirmations a ytwg suggested but there are no callbacks for the second transaction.
For the first you mean ?
The first is the transaction from customer to receiving address, the second is the one from the receiving address to my address right ?
But ok i see, wether I wait for the second transaction to confirms and callbacks, or I manually check confirmations of the first transaction.