Pay Instruments to Default to specific GL bank accounts

How do I go about setting up a specific pay instrument to default to a specific GL Bank Account?

For instance I have a Payment instrument of "A" with a GL Bank Account that currently defaults to 005

But I want all my "A" PIs to default to GL Bank Account that ends with 200

AAI current default - 1000.1120.005

Want Pay instrument "A" to default to 1000.1120.200

Regardless of whether the payment is automatic or manual.

Is there a document out there that will guide me through this type of setup?

Thanks-Regards-NA