Formula to calculate on a quarterly basis the fee due based on the % threshold it's c

Help!

I'm not sure if this is possible or not?

Basically every quarter I must submit a fee to my head office based on 2 variables - profit & YTD profit conversion %

Now I calculate these figures monthly semi-manually and put them into the table attached.

However the fee I must submit is based on the profit per month * 7%, and then the YTD proft conversion % is used to calculate whether I pay the full fee or 50%, 65% or 80%

Over the course of a year this conversion % goes above cetain thresholds and also below which makes it more difficult for me to think how to do it?

What I really need is a formula to calculate on a quarterly basis the fee due based on the % threshold it's currently in, but this formula will also have to take into account the overall YTD% and fees paid so that if the % level drops then I'm either not over/under paying

I know this is a really bad explanation, so I've atatched a test spreadsheet which shows what I'm talking about

Any help greatly appreciated

Thanks