OK so you tried to post some code but you missed the mark. The code you posted is full of syntax errors and variables not declared. There are columns referenced in your table that don't exist, etc. It seems you must have tried to simplify this but it just didn't work.

I don't understand what you mean about calculating interest. There are a lot of ways to calculate interest and we still don't know how you are doing it.

The while loop could be greatly simplified to a single insert statement instead of looping but getting this to work is incredibly difficult because none of the ddl supplied matches the insert and such. In short, if you can provide something that is more accurate we can help with the calculations but as it sits it doesn't work. As you provided it, it will not even compile.