Hi,

this is for version 10.

var Model = require('web.Model');

new Model('custom.model').call('write', [[self.id], { 'invoiced_target': value }]).done(function() {

});

call 'write' or other function which exist. 

so whatever value you pass in '{ 'invoiced_target': value }' value you will be able to get in python  method of  'custom.model'.

so you will be able to get value from  python function and write the value in the field.

Regards,

Silvestar