Report Rule Action - Aggregate Multiple Values from Report

We are using a report rule to send remittance information to suppliers upon payment. I am attempting to provide details in the body of the email with an aggregate list of Invoice ID’s using the following expression. 

[@UNIFORM_PAYMENT_ADVICE_REP/IDENTITYS/IDENTITY/ADDRESS_IDS/ADDRESS_ID/PAYMENT_DATES/PAYMENT_DATE/DETAILS/DETAIL/INVOICE_NO]

The XML is listed like so 

<DETAILS>
    <DETAIL>
        <DISC_AMOUNT>0</DISC_AMOUNT>
        <FULL_AMOUNT>100</FULL_AMOUNT>
        <CURRENCY>USD</CURRENCY>
        <INVOICE_DATE>2025-11-25T00:00:00</INVOICE_DATE>
        <INSTALLMENT_ID>1</INSTALLMENT_ID>
        <PAYMENT_REFERENCE xsi:nil="1"/>
        <REMITTANCE_INFO xsi:nil="1"/>
        <INVOICE_NO>SI11-25-2025-1</INVOICE_NO>
        <PAYMENT_AMOUNT>100</PAYMENT_AMOUNT>
    </DETAIL>
    <DETAIL>
        <DISC_AMOUNT>0</DISC_AMOUNT>
        <FULL_AMOUNT>100</FULL_AMOUNT>
        <CURRENCY>USD</CURRENCY>
        <INVOICE_DATE>2025-11-25T00:00:00</INVOICE_DATE>
        <INSTALLMENT_ID>1</INSTALLMENT_ID>
        <PAYMENT_REFERENCE xsi:nil="1"/>
        <REMITTANCE_INFO xsi:nil="1"/>
        <INVOICE_NO>SI11-25-2025-2</INVOICE_NO>
        <PAYMENT_AMOUNT>100</PAYMENT_AMOUNT>
    </DETAIL>
</DETAILS>

I would like to have the expression in this example output

SI11-25-2025-1, SI11-25-2025-2

Any help would be greatly appreciated. 
Thank You!