implementing a matlab function in simulink to get the distance from an ultrasonic sensor

I am trying to use the matlab function block in simulink to get the distance from an ultrasonic , I used the HC-SR04 Add-On Library for Arduino this was my function

function [distance,time_c] = ultrasonic(trig,echo)

a = arduino('COM13','Uno','libraries','JRodrigoTech/HCSR04');

sensor = addon(a,'JRodrigoTech/HCSR04',trig,echo);

time_c = readTravelTime(sensor);

distance = readDistance(sensor);

end

however it seems that I can't build the arduinon object inside the function how can I achive that ?

I am new to this , if you have a link that can help