Compound interest

Hi Experts,


Can you please provide some help.

I know how to do regular compound interest formulas however this one is a little strange.

Months 1 and 2 are strait interest on the principle (starting) balance.
Months 3 onward is compounded.
Example Months 3: = (Principle balance + Interest on Month 1) * interest rate
Example Months 4: = (Total Balance (Month 3) + Interest on Month 2)* interest rate
Example Months 5: = (Total Balance (Month 4) + Interest on Month 3)* interest rate

Please see the attached example.

I would like a Vba or formula that can tell me the total interest base on the month variable.