You need a valid self join type of relationship for this to work. I don't use this kit, so am not familiar with the table/relationship design for this database system. When you open Manage | Database | relationships, you'd need two instances invoices linked by a unique key field (usually an auto-entered serial number). Then you can use GTRR in this fashion, specifying the name of the 2nd table instance.
All you really need is:
Go To Layout [Print Format Invoices]
Since both layouts refer to the same table, switching layouts should leave the same current record visible on both.