what you are asking for is a mechanism to tentatively add a transaction and then dispute it later.
I don't think that's what he means. The transaction will be made completely, but both will hold part of the key required to spend that money. If they are satisfied they ship the money to the appropriate person. There is not disputing with the block chain. They either work it out and use the code like everyone else does for all transactions, or they don't work it out and the money stays locked up.
if the buyer refuses to finalise the transaction and the seller refuses to permit a refund, they have 2 choices.
1) be spiteful and nobody will get anything
2) agree on a third party to send the money to. that third party will be an arbitrator who will weigh up both sides of the argument and come to a decision as to who should be returned the money, minus whatever fee they agreed with the two hurt parties.
Subsequent to this, I also realised that my suggestion is open to trolling whereby a seller makes someone do an escrow transaction and then refuses to ship anything or arbitrate, my solution to this issue gives the following modification of the system:
the buyer makes an escrow transaction which is then presented to the seller, if the seller wants to go ahead, they must agree to be debited a sum stipulated by the buyer, the seller agrees and the escrow transaction then goes into the network for inclusion into the block chain, both parties are now down on their money.
if everything goes to plan, the buyer OKs the release of the funds and the seller gets the payment + his "trust deposit" returned.
if the buyer wishes to cancel, the seller authorises the cancellation and both parties get their original funds back.
if nobody can agree on a release, both parties now have an incentive to go to an arbitrator, when the arbitrator is authorised to receive the transaction funds, the trust deposit gets immediately returned to the seller, the arbitrator doesn't get a say over those funds.