If yoyu have a FSU in your system, you could force the speed to zero, when the Lightcurtain is broken, and when It's okay, use normal speed, in that way the robot will stop every time you break the lightfence, and start automatic, when the fence is OK!
Thanks kinguno!
I will check on the FSU. Is there coding that has to be added to a program or is it a monitored input on the safety unit that automatically puts the speed at zero? I have not messed around with the FSU before but this sounds like a great option to use.