Need help callculating compound interest on a judgment wihich has sporadic non-uniform payments received and calculate per diem interest\

[Kent O]

I am trying to create a spread sheet that will take a legal claim amount, add court costs and recoverable expenses to get the total judgment amount, and then apply a varied percentage (based upon the percentage of attorney fees awarded-hopefully with the ability to "set" the attorney fee owed by the debtor so that it will only withhold that amount) of each payment to COSTS, INTEREST AND THEN PRINCIPAL in that order. I currently have a sheet designed in table form that receives the payments, applies the percentage based upon a drop down menu that chooses the amount of fee awarded.
I greatly appreciate any help.
Kent