GoalSeek VBA freezing up

Looks like a different facet of this problem: https://www.excelforum.com/excel-pro...ecxceeded.html If the algebraic suggestion I make in the other thread would work, then Goal Seek will not be needed at all, an the problems caused by Goal seek diverging to unreasonable numbers will also go away. Check your other thread and indicate whether or not an algebraic solution will work for you or not.

I have to set objective m3 to value of "blank" but the value I want is what value the user enters in e3.

I don't follow you on this. You should be able to enter whatever value you want into the "to value of" field. Perhaps you are referring to the "feature" that prevents you from entering a reference to a cell in this field. I usually sidestep that problem by formulating the objective function to be =current formula in M3 - E3 then set M3 to a value of 0.

The reason an algebraic solution will not work is because I have two unknowns and one equation.

I must have not understood the spreadsheet, then, because I saw only the one equation and one unkown. Either you are solving for E3 at G3=100 (for the data validation rule), or solving for G3 at E3=entered value (and using data validation to make sure that this cannot be above 100). What am I misunderstanding?

Why not just use a formula in G3?

=(C53 - E3*G53) / (E3 - 8.33)

If you have one equation in two unknowns, there isn't a single solution ...

I did not see the "circular reference" between G3, C53, and B45. How does your spreadsheet handle the circular reference created when B45 is not 0 (I assume it will always be between 0 and 1)? As one who usually has iteration enabled, it seems to calculate the values of C45, J45, E45, C53, and G53 just fine with the simple "successive approximations" algorithm that is currently built into the spreadsheet, though I have no reference for knowing if it is converging on the correct value.

Having C53 and G53 be functions of E53 does not introduce a new unkown. It simply makes the algebra more complicated. G3 should still be a straightforward function of E3. The main complication seems to be solving the equation exactly for the minimum value of E3 (that makes G3=100). I noted that, solving the equation for E3 as if C53 and G53 are not functions of E3 still seems to give a pretty close value for the threshold value for E3, and may still be useful. Or, as I suggested, simply use G3<=100 as your data validation criteria and don't worry too much about solving exactly for E3