Hello, for one of my project, i had implemented the same logic, an i was used one of the custom module for fulfilling my requirement. Here am sharing the module info. you can check and use it.

https://apps.odoo.com/apps/modules/13.0/salesperson_sales_target_app/                                                                               

User can create and track sale target for each salesperson and also send email to a particular sale person with targeted details. And this module providing some needed validations. When we confirm the  SO against one customer, sales target will be updated. The main benefit for using this module is that it  provided option to achieve target based on sales order confirmation, delivery order, invoice creation or while invoice is paid.