While you can't officially do this according to the rules, I've gotten around this by trading "deposits". In other words, for your trade I might trade two sheep

While you can't officially do this according to the rules, I've gotten around this by trading "deposits". In other words, for your trade I might trade two sheep for one wood and one ore, and later trade one ore for three brick. That way there are two separate trades and you're not just giving me brick on a later turn to satisfy a previous trade. The flip side of this, of course, is that there's nothing stopping you from welching on the deal later, aside from the normal game-theoretic reasons you may not want to screw someone over. So I'm incurring significant risk this way.