Linking Comboboxes

[MrP]

self.cboCust['values'] = (fill_custbox())
self.cboCust.bind('<<ComboboxSelected>>', fill_addrbox)
self.cboAddr['values'] = (fill_addrbox())
Exception in Tkinter callback
Traceback (most recent call last):
File "D:\Python 3.7.9\lib\tkinter\__init__.py", line 1705, in __call__
return self.func(*args)
TypeError: fill_addrbox() takes 0 positional arguments but 1 was given

But if I put event in like this def fill_addrbox(event): I get this:
builtins.TypeError: fill_addrbox() missing 1 required positional argument: 'event'

and then if I put event here: self.cboAddr['values'] = (fill_addrbox(event)) I get: builtins.NameError: name 'event' is not defined