Maximizing (Complicated Problem)

I have attached my spreadsheet for reference. I'll try to be as brief as possible,

I am building a bond payment spreadsheet. Cash inflows are received over time which are used to pay a) "base bond interest"; and b) "additional bond payments" (which in turn are separated into additional interest and principal payments)

After the bondholders have received a specified IRR (cell: C43), the remaining funds are distributed to the issuer (cell: AM 40). I want to change the "additional bond payments" amounts to maximize AM40 (the amount distributed to the issuer). However, I have one constraint: the cash balance after interest payments (row 38) must be greater than or equal to cell C44.

I have tried a variety of methods including solver, premium solver, formulas, and recorded macros. None seem to work for a variety of reasons.

Any help would be greatly appreciated. Thank you in advance