So I'm working with a machine that has a parameter on the HMI (EZ Automation EZ-T10C-F)that writes back to F11:17 on the PLC (SLC 5/04). The problem is the operator shouldn't be able to change this, a new operator did just that and goofed it up, took a while to figure out what happened. I do not have the software to alter the HMI program so that is out. Is there a way to make that address "locked" so if they try to change it from the HMI it won't actually write the change? Worst case I'll change the program so that it uses a different address all together but I'd rather not change the program if i don't have to. Any help is greatly appreciated.