DAVID - re your comments re excel
I am obviously late to the show as far as your fantastic efforts to ' solve" a multi-variable problem using excel iterations, etc. But perhaps - just perhaps the use of a unique addon to excel may help
Its called solver
https://support.office.com/en-us/art...B-F63E45925040
Applies To: Excel 2016 Excel 2013 Excel 2010 Excel 2007 Excel 2016 for Mac Excel for Mac 2011
Solver is a Microsoft Excel add-in program you can use for what-if analysis. Use Solver to find an optimal (maximum or minimum) value for a formula in one cell — called the objective cell — subject to constraints, or limits, on the values of other formula cells on a worksheet. Solver works with a group of cells, called decision variables or simply variable cells that are used in computing the formulas in the objective and constraint cells. Solver adjusts the values in the decision variable cells to satisfy the limits on constraint cells and produce the result you want for the objective cell.
Put simply, you can use Solver to determine the maximum or minimum value of one cell by changing other cells. For example, you can change the amount of your projected advertising budget and see the effect on your projected profit amount.
or
use of the scenario or solver or goal seek stuff may save you a lot of time
just perhaps ???
