send angle to stepper motor via serial arduino and simulink

without serial when i constantly change to desire angle motor goes to desire angle and stop i want to send the angle via serial to Arduino i made this serial receiver block and set everything and send also but i noticed that motor go to the angle and back to zero and same for every sample time i asked my professor he suggest making it check from status and make a function to check if zero and the past angle it it out but i tryed with this and cant made this function block can you please help me i will attach all files here