No current field.
You've used the old() or diff() functions in a script, but there's no current field specified. These functions can be used only in the change script for a window field. Both functions use the current field to indicate the field's previous value or the differences between the field's new and old values. These functions won't work in procedures.
Be sure you're using the old() or diff() functions in the change script for a field in the current window.