Closing the Credit Notes while making a Customer Refund

Dears,

We have a requirement where Customers need to refunded his/her Credit Balance.

We have defined Receivable Activities and Receipt Methods and we are successful to make the Refunds following seeded functionality.

But, the credit memos are remaining open because once we select 'Refund' in apply form, it doesn't allow to select any transaction as intended functionality.

Please let me know, if there is a way to close such credit notes.

Please note that we are not using Auto Invoice program.

Thanks in advance.

Regards

Jayashis