Object Oriented Design Vs Procedural

Our company currently uses an APL model to illustrate our life products. We are in the process of converting this to Excel/VBA because the APL system is extremely difficult to maintain.APL is difficult to maintain because the code has become over the years (~15yrs) spaghetti and only a select people (who have worked here 5+years) really understand this to make updates when new products come out. APL is also not well known and difficult to understand. I just would like help on designing the system, my main career is not a programmer, and the design I was envisioning was a "Procedural" approach. (the APL is procedural rather then object oriented. I have not used object oriented code before)Basically the program illustrates a life insurance product. That just means it projects a fund out from the time the policy is issued to age 120. The illustration is given to the policyholder as a way of predicting what the value of their fund will be given some assumptions.The program does the following1.) Populate Variables2.) Calculate Premiums Types3.) Monthly processing4.) Output values to spreadsheetThe system has to illustrate different types of Products and we are adding new products to the system. Most of the main structure of the program (in VBA) is already written. It seems that (#3) monthly processing will vary by product, and I would like help with maintaining that part of the code. The other 3 parts of the program are not a problem maintaining.We will be continually adding products. We will start with about 5 products and maybe add about 5 per year.Here is the Monthly Processing code:... Call MonthlyProcessing(120, PremPayMode0, Assump0, True, DumpLumpSum0)