A Mas'ala!

The animal of Qurbani should already be yours before its blood is shed, otherwise your Qurbaani will not be valid. For that animal to become yours, you must have bought it already before it is slaughtered. If the price of the animal was not yet fixed at the time of its slaughtering, it means that the animal was not yet yours. It still belonged to its owner. That is why we should be very careful. Many people are of the habit of fixing the price of the animal according to its weight after slaughtering. They do not fix the price before that. Thus, this means that when the animal is being slaughtered and its blood is being shed, it did not yet belong to those who have taken share in the Qurbani animal. Therefore, this is like buying meat at the butchery. That is why the Qurbani is not valid in this way. 

[English version of "Bizin fini faire prix zanimau ki pou faire Qourbaani avant coupe li! " – Al Jamiat – Vol.3 No.11]