find the royalty value that each band contributes

I'd be so grateful on the easiest way to do this the most efficient way - I'm sure it's a classic!

I have a Revenue, say R which can vary from 0 to some large value. I also have a table

Band Min Max Royalty
Band 1 0 50,000 40%
Band 2 50,001 100,000 35%
Band 3 100,001 200,000 30%
Band 4 200,001 400,000 25%
Band 5 400,000 - 20%

I want to find the royalty value that each band contributes. I also need it generalised so that I can change the min/max values in the bands and the royalty figures.

Thanks in advance.

Try looking here