And there is a relationship linking Customers to Invoices?
If such a relationship exists:
Customers::__pkCustomerID = Invoices::_fkCustomerID
Then you can put the Invoices::_fkCustomerID on your Customer layout, enter find mode and specify a lone * in the _fkCustomerID field.
Can this be alternatively be done via relationship and TO instead of performing a find request?
Go to the Invoices layout.
Show all records.
Use Go to Related records with the "Show only related records" and "match found set" options specified to pull up all related records in Customers.
I will test these 2 ways of doing it.