OAF customization in iSupplier Create Invoices to not allow attachments to be added to approved or p

I am creating a new controller extending InvoiceRequestPGCO. I would like to grey out the add button when the invoice has been approved or paid. I have written a function to check this.

I see that the view object is InvReqListVO.

There is a list of invoices. At the far right, there is an OAFlowLayoutBean, I believe called 'Attachment', with 2 icons, one to view attachments and one to add attachments.

For each row in the list of invoices, I am checking to see if the invoice is approved or paid. This is working, as I am writing a record to a custom table for each row in my function.