-plotstamp User Fields not saving changes

[metal_pro2]

I'm trying to modify the plotstamp User Fields from the command prompt (not the dialog box version of the command)

I type this at the command prompt

Command: -PLOTSTAMP
Enter an option [On/OFF/Fields/User Fields/Log file/LOCation/Text Properties/UNits] : U
Enter user field 1 <>:Job #WXYZ
Enter user field 2 <>:
Enter an option [On/OFF/Fields/User Fields/Log file/LOCation/Text Properties/UNits] :
Command:

Howevere the values for user field are not saved ? They are blank or unchanged

The dialogue box version of the command works fine but I want to use the command prompt version of the command so it can be used with some automatic scripts