How do I create a spreadsheet to accrue interest on a balance 30+d

[dowwcoww]

My ex is obligated to pay 68% of our daughters' medical costs. He has not
paid anything for over 3 years. If he owes me $10 on a copay, he has 30 days
to pay me back. If he does not pay me back after 30 days, I am allowed to
charge him 5.5% annual interest on the owed amount. I need to calculate how
much he owes me after 1 month, 2 months, 3 months, up to 72+ months. May I
please get help with creating this spreadsheet so that all I have to do is
input data monthly? Any and all help is greatly appreciated!

 

[FloMM2]

dowwcoww,
Here is what I came up with:
In Cells B1 thru BI1 "1-Month, 2-Months,etc."
In Cells N2 the BI2 "25-Months, 26-Months,etc"
In Cells B3 thru BI3- format to "Currency" and two decimal places.

In Cell A2 "Medical costs"
In Cell A3, format is "Currency" with 2 decimal places, I enetered "$100.00"

In Cell B3, "=FVSCHEDULE(A3,(5.5/12)%)" . This calculates the interest (5.5%
annually) for $100.00 dollars. 5.5 is divided by 12 because it is one month.
I next copied B3 across to BI3. This way it compounds the interest and the
"ex" owes what is not paid the previous month not just what the original
amount was.

Hope this helps, and good luck.