Of conflict is interpersonal and the two employees seem a bit heated. You would pull them away into a new environment and get each of them to explain the matter cordially. From the info you have heard you make a decision whether it to side with one over the other or make it a win-win situation or alternatively if the matter can not be redesigned then you would create a lose-lose situation in which you explain the loses they would both go through if it has to be changed and come to an agreement.