Is it possible to iterate within a simscape block in the equations section?

I am writing a custom block where I do not have a closed-form solution for one of my parameters. For example, in order to find parameter P, I need to make a guess, calculate another value based on that guess using tablelookup, check it against another parameter, and if it is not within a certain tolerance range, make a new guess for P and repeat. Is it possible to do this in the 'let' portion of the equations section? If not, is there another way to accomplish the same functionality?