One of several independent brokers employed to procure a purchaser must produce a customer of his own, and not one then sustaining that relation to another of the brokers, and when he is first in negotiating with a customer he will continue to sustain that relation until it is expressly broken off or the matter of the purchase has ceased to be held under consideration by the purchaser. Jennings v. Trummer, 52 Oregon, 149, 96 P. 874. Compare Sec. 445.