formula for commissions on a per piece bases

[LMM300M]

I am looking for a template or calcuation for piece work sales commission
payments.
i.e. 1-100 gets paid at .10,
101-200 gets paid at .20 etc.
so a person selling 150 would get paid
100 * .10 for 10
50 * .20 for 10
for a total of $20.00
drawing a formula blank at the moment.

 

[Toppers]

If there are only two rates, then general formula would be:

=sales*rate1 +(sales-100)*(rate2-rate1)

=150*0.1+(150-100)*(0.2 - 0.1)

=15+5

If there is a range of rates look here:

http://www.mcgimpsey.com/excel/variablerate.html