Need help! Fanuc S420 i W to stop between two points if sensor is activated

Hi there, it's my first time programming and I'm running into a bit of trouble. Currently programming an old welding robot to palletize stacks of eggs, but I also need it to de-palletize another pallet with variable height. I want the robot to stop between two linear points if a proximity sensor is activated, but I can't seem to find out how to program this using the teach pendant. Could someone help me out? Thanks in advance