Optimize quantity of cell (volume) until another cell (funds) reaches Minimum tolerance

Good day,

This is my first post/thread. Pardon my inarticulate way of explaining the problem.

CONTEXT:

I have a proforma cash flow spreadsheet.
Columns represent consecutive months.I have 60 consecutive months (5 years) with totals in between. It is structured in following order:
Month 1; Month 2; Month 3;...etc....Month 12; TOTAL YEAR 1 Month 1; Month 2; Month 3;...etc Month 12; TOTAL YEAR 2 >> all the way to year 6.

Rows are structured in the following logic:

ROW 30 >> OPENING BALANCE (cash)

ADD >> ROWS 32-40 >> INFLOW (Cash in)

SUBTRACT >> ROW 42 = SUM of 43-50. So it it the TOTAL CASH OUTFLOW.
ROWS 43-50 >> OUTFLOW (Cash out)

EQUALS >> ROW 52 >> CLOSING BALANCE

The next column (month) then starts its opening balance (row 30) equals to the closing balance (row 52) of the previous column (month).

Straightforward cash flow model.

PROBLEM:


ROW 24 is the variable that I require help with.
ROW 24 contains the tonnage (monthly volume) I want to / am able to sell for the month. This is multiplied by the cost price and contributes to the total OUTFLOW (ROWS 42).
ROW 42 determines in turn the final ROW 52's value which is the closing balance.

I don't want the value in row 52 to ever be under $40,000.00 for a respective month.
I therefore have to keep adding/subtracting row 24 (the volume) until I hit the "sweet spot" (the closest value above U$40,000.00)

QUESTION:

How do I run a Macros to "loop" (or something?!) until each respective month's minimum fund amount (U$40,000) has been reached.

Hope this makes sense.