Stop the Movement of the Robot on Low Obstacles

A robot with an Arduino Uno board and an L293 engine with a control shield, on an analog A0, A1 is a pinned ultrasonic sensor, IR MH-8 sensor I would just like to stop the movement of the robot on low obstacles. I need the code for this command, because I get an error "ProxSensor was not declared in this scope". IR sensor hawe "Vcc, gnd and out". "Out" pin of the sensor gives value "high or low" which would send a signal to the dc motors on the shield, "Stop or go".

We can't see your code

If I wrote a code or sketch, I wouldn't even ask for help,
give some code as a suggestion, the idea for the project is there, it just needs a little knowledge