Excel diverges during iteration

Hi there.

A picture is worth 1,000 words. An Excel sheet is worth 1,000 pictures.

Please read the yellow banner at the top of the screen. Act on its guidelines and post a SMALL sample sheet. It does NOT have to be your real sheet. Mock up a sample.

Your description feels incomplete, as I don't understand exactly what solution you are trying to get. Some unrelated, unorganized thoughts:

A look at the algebra of the problem suggests to me that the row of calculations can be rewritten to eliminate the circular reference. It doesn't change the result, suggesting that the circular reference is neither contributing to or hindering the solution. I can change G11 to =$C$6+SUM(F12:F77) and the results are exactly the same but the circular reference is now gone. Not know exactly how this snippet fits into the larger spreadsheet, I can't say for sure exactly how to eliminate the circular reference in your real sheet (or if it is even possible). It might be worth some time/effort to see if you can eliminate the circular reference.

I notice that you do not include any error trapping in your circular reference loop. I find that I almost always want some kind of "reset on error" trap in the loop to catch any errors and prevent them from killing the loop. Something like =IFERROR(circular reference formula,reset value) somewhere in the loop. Again, since I don't understand exactly what your calculation is doing, it is difficult to recommend a specific formula.

The idea of starting C4 at some value (60000) and adding 1000 until C4 is 80000 sounds more like a data table operation to me (https://www.excel-easy.com/examples/data-tables.html if you are unfamiliar with data tables). To illustrate, I put 10000, 20000, 30000, etc. into N2:N9. Enter =D11 into O1 and copy into P1:S1. Then select N1:S9, call up the Data Table command, and put C4 into the column input cell field. Upon pressing OK, the table should fill in with the appropriate values -- with or without the circular reference.

It's not much, but maybe one or more of those ideas will help point you to a solution you can work with, or allow you to explain your exact problem better.