How to get an if function to work with a mileage limit cut off - last bit of formula not quite there!

I've got a file to calculate mileage which I can nearly get working.. The idea is that when a cumulative amount exceeds a limit, then some of the mileage will be at a rate for below the limit and another for the rate above the limit. On the week, that the limit is crossed, the lower limit rate is paid for the miles up to the limit and then a different rate kicks in for the balance.
EE_mileage_one_band01.xlsx