It seems the special treatment of the first input field can be avoided by doing a DISABLE(318) in the before-field logic.
However, this has the unwanted side effect that cancelling no longer exits the LS!
So one also needs to have the following logic at the start of the first field's general-check.
CHECK-INPUTThen I think things seem to behave pretty much as desired (but I haven't thought about it for long).
IF @FNKEY = @CANCEL OR $INPUT = '/' THEN LSEXIT ;
Whether anyone in their right mind would use such an undocumented feature is a different question of course