I need to calculate percentage rent owed when their are multiple percentage
rent rates with different breakpoints. The formula below returns "False" if
N20=0.

=IF($N$200,IF(I13$M$20,(I13-$M$20)*$N$20+($M$20-$M$19)*$N$19+($M$19-$M$18)*$N$18,IF($N$190,IF(I13$M$19,(I13-$M$19)*$N$19+($M$19-$M$18)*$N$18,IF($N$180,IF(I13$M$18,(I13-$M$18)*$N$18,0))))))

Where N20 = % Rate 3
N19 = % Rate 2
N18 = % Rate 1
M20 = Breakpoint 3
M19 = Breakpoint 2
M18 = breakpoint 1
I 13 = sales