if(sum("Deals"."Deal Size") < 0,0,if(sum("Deals"."Deal Size") < 50000,.03*sum("Deals"."Deal Size"),if(sum("Deals"."Deal Size") < 100000,1500+.05*(sum("Deals"."Deal Size")-50000),4000+.07*(sum("Deals"."Deal Size")-100000))))
Pick apart what this means and try something like it yourself!