Good morning,

Nice to meet you all and this is my very first post. I have been using excel for ages, but now I am facing a real problem and I don't know if there is a solution.
I am doing a model and it is divided into a number of steps. In each of the step, there are some iterative calculations until they converge, and the outputs of one step are the inputs for the following one. With a little number of steps like 3-4 I can change the model as much as I want and it is robust. However, when it comes to a higher number of steps (11), it becomes really sensitive and it collapses with a small change in the overall conditions. Sometimes the errors are #DIV/0 or #NUM, I think it is related to the accuracy and the number of iterations, because it also slows down a lot from step 8-9. I have the maximum amount of iterations (9,999 I think) and the maximum change has to be really small because I use some properties that the magnitude order is 10-5.

Do you have any suggestion, any idea what could be wrong or any program that could be better to do these calculations? It is worthy to mention that there are no macros at the moment and there are divisions, multiplications and trigonometric functions and some numbers to the power of X, and X could have almost any value. All the cells are checked to not be divided by 0.

Many thanks and kind regards,
Jorge