Hallo Everybody ! I have tried to look in the previous posts, but I haven’t find something useful. I am looking for an iteration function to help me to solve following issue. I have got three values, let’s say A which is a constant (it is determined), that can be positive, negative or 0 B which is variable that can be positive, negative or 0 C which is variable that varies between two fixed values (typically 0 and 1). The scope of the function would be to vary C in order to get B as close as possible to A. C and A are not linked by any relation, let’s say that A is a target value. C and B are proportional, but they are not linked by a known function. Therefore the algorithm should : Vary C of a value, then verify the error between A and B and should this error be positive or negative, vary C consequently. I hope to have been clear enough. Is there anybody who knows a similar algorithm ? Many thanks for your help !