How can I use fminsearch inside a Simscape component's source code?

I'm trying to use the fminsearch function to help set parameters for a custom Simscape component. However, when I try and load the code, I get an error that there's an "unexpected @". In fact, I can't seem to use a function handle at all within Simscape, so I therefore can't use fminsearch. Is there any way around this? Or an alternative that works?

[Walter Roberson]

All I find at the moment is https://www.mathworks.com/matlabcentral/answers/502654-solve-a-non-linear-equation-in-simscape